NYCU-TUAT-UY Symposium 2023

INV. 01

Stimulated Raman Scattering Microscopy
for High-Contrast Drug Imaging
Terumasa Ito
Department of Biomedical Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo, Japan
Author e-mail address: teru-ito@cc.tuat.ac.jp

Abstract: Real-time, quantitative measurements of a small amount of drug in tissue imaging
by conventional Raman microscopy remain challenging. I present a novel stimulated Raman
scattering (SRS) microscopy method with increased signal contrast using phase-modulation(PM) and temporal optical filtering. In addition to removing nonlinear background signals
with PM, the new microscopy can also reduce intrinsic tissue Raman background signals by
temporally separating the excitation and detection processes.
1. Introduction
Noninvasive and label-free laser measurements that acquire information in cells and tissues are applied in many
fields of life science and medicine. Raman microscopy, which is based on the frequency characteristics of lightscattering mediated by molecular vibration (Raman spectrum), is a promising label-free method for observing
pharmacokinetics of small-molecule compounds. However, conventional Raman microscopy does not support
real-time analysis due to its weak signals. To address this problem, advanced Raman microscopes utilizing
nonlinear effects such as stimulated Raman scattering (SRS), which greatly enhances the Raman signal using
pulsed optical excitation, have been developed [1]. While SRS microscopy enables high-speed imaging of living
cells and tissue, it is still difficult to quantify a small amount of small-molecule drug. This is because the signalof drug molecules at low concentrations, such as those present in living cells and tissue, is often weak comparedto the background signal. Typical background signals that hinder measurement include the non-Raman signals
derived from nonlinear effects (such as cross-phase modulation), and the false Raman signals from the living
tissue itself. To suppress these unwanted signals, several background suppression methods based on differential
spectral detection such as frequency-modulated SRS detection have been proposed [1]. However, quantitative
drug measurement remains challenging with the previous methods because differential spectral detection
produces large baseline offsets, especially when a steep spectral background overlaps the target signal peak.
We developed a new SRS microscopy method with phase-modulation (PM) and temporal optical filtering[2-3]. In addition to removing the nonlinear background signals using PM detection, the new SRS microscopy
can reduce tissue Raman background signals by temporally separating the excitation and detection processes.
With this new approach, quantitative drug measurement with a high signal-to-background ratio can be achieved
even when the concentrations of the drug molecules are below a few mM in tissue.
2. Results and Discussion
Figure 1 shows a demonstration measurement of drug
penetration into skin tissue. To implement the temporal
optical filtering, we used a pump−probe scheme with
impulsive excitation (pulse width <15 fs) and temporally
delayed (delay: 1.7 ps), asymmetrically shaped
picosecond pulses, which enables selective detection of
the long-lived vibrational signals from the drug
molecules. Two topical pain-relief drug solutions(lidocaine hydrochloride: LID, loxoprofen sodium:LOX) were applied to a skin tissue model (Epiderm Epi606X, Mattek), and the subsequent drug penetration wasobserved by depth-resolved SRS and confocal reflection
imaging. The results showed that the contrast
enhancement over conventional SRS was > 40 times, andthe limit of detection in tissue was at several mM.
Fig. 1 SRS imaging of drug penetration into skin tissue:(top) depth-resolved imaging using combined confocal
References[1] J. X. Cheng, W. Min, Y. Ozeki and D. Polli, Stimulated Raman
Scattering Microscopy: Techniques and Applications, Elsevier (2021).
[2] T. Ito, Y. Obara, and K. Misawa, APL Photon. 3, 092405 (2018).
[3] T. Ito, R. Iguchi, F. Matsuoka, Y. Nishi, T. Ogihara, and K. Misawa,
Biomed. Opt. Express 12, 6545-6557 (2021).

reflection and SRS, (middle) 30 and 240 minutes after
topical application of 148 mM LID, and 131 mM LOX(LID at 1092 cm-1, LOX at 1184 cm-1, scale bar: 50 μm),(bottom) monitoring of drug concentrations in tissue,
showing that the LOX was more permeable to the skin.

NYCU-TUAT-UY Symposium

INV. 02

Few cycle THz dual-pulse generation and manipulation
technique with a high degree of freedom
Hao-Keng Wei1†, Zai-Wen Chen1, Yu-Ting Lin1, Hironori Ito2, Kazuhiko Misawa3,4, Chih-Wei Luo1
1
Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan.
Graduate Faculty of Interdisciplinary, Research Faculty of Engineering, University of Yamanashi, Japan.
3
Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo, Japan
4
Department of Biomedical Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo, Japan
Author e-mail address†: ihatetomato.sc05@gmail.com
2

Abstract: In this study, we demonstrated the THz dual-pulse generation via a modified
Michelson interferometer (MI). Comparing to the traditional methods of field control technique,the architecture we proposed here has many advantages such as higher damage threshold, higher
tunability, the ability to scale to multi-pulses, etc. Furthermore, we proposed the f-t modulation
technique to manipulate the THz dual-pulse via only two parameters. Such novel system showshuge potential for applications, not only in imaging and spectroscopy but also in next-generation
communications.
1. Introduction
Field control techniques play a pivot role in many fields such as spectroscopy, imaging, and communications.
Our previous work [1] proposed the modified MI system to generate the polarization twisting pulse/dual-pulse(PTP/PTDP) as the light source, which gave high degrees of freedom such that one can arbitrary manipulate thetwisting frequency, helicity, and interval between dual-/multi- pulse. Based on this technique, we utilized such
PTPs/PTDPs as light source to generate the THz pulses by utilizing an EO crystal (e.g., the GaP crystal in thisstudy) to perform a second-order nonlinear process [2,3].
2. THz generation via PTPs/PTDPs formulism
To characterize the PTPs/PTDPs, the zero-phase diagram is introduced, which indicated the relation between
frequency and time delay of a pulse. Such conceptual diagram helps us to realize the key characteristics of a
PTP/PTDP such as the rotation frequency and helicity, and straightforwardly links the key parameters of systemand pulses such as the first-/second- order dispersion and the position of optical elements.
A PTP can be model by the combination of a right-handed circularly polarized (RHCP) pulse and a lefthanded circularly polarized (LHCP) pulse as:d𝜔 −𝑖𝜔𝑡1d𝜔 −𝑖𝜔𝑡
1
𝐸x (𝑡){=∫𝑒𝐸𝑖 (𝜔)𝑒 −𝑖𝜃𝑐 [ ] + ∫𝑒𝐸𝑖 (𝜔)𝑒 −𝑖𝜃𝑐 𝑒 −𝑖𝜃𝑝 [ ] ,(1)𝐸y (𝑡)2𝜋𝑖
2𝜋−𝑖where 𝐸𝑖 (𝜔) is the spectrum of the initial laser pulse. 𝜃𝑝 and 𝜃𝑐 are the chirp introduced by first- andsecond- order dispersion (γ, β) from the system, formulated by 𝜃𝑝 = 𝛾(𝜔 − 𝜔0 ) and 𝜃𝑐 = 𝛽(𝜔−𝜔0 )22
T.

By calculating the second-order susceptibility of a GaP crystal, the polarization 𝑃 = [𝑃𝑥 𝑃𝑦 ] induced by a
PTP normally incident onto (1 1 1) plane can be shown as [4]:𝑃𝑥
4
−𝐸𝑥 𝐸𝑦∗ − 𝐸𝑥∗ 𝐸𝑦[ ]=𝜖0 𝑑14 [],(2)𝑃𝑦
𝐸𝑦 𝐸𝑦∗ − 𝐸𝑥 𝐸𝑥∗√6
where 𝜖0 is the vacuum permittivity, and 𝑑14 EO coefficient of GaP crystal. 𝐸𝑥 , 𝐸𝑦 are from equation (1), and 𝐸 ∗represented the complex conjugate of 𝐸.
3. Conclusions
In this study we demonstrate the THz generation from PTPs/PTDPs with a high degree of freedom numericallyand experimentally. A conceptual zero-phase diagram is introduced to characterize the PTPs/PTDPs, which canbe helpful and straightforward to manipulate the PTPs/PTDPs and corresponding THz (dual-)pulse. Such lightsource shows a huge potential in imaging, spectroscopy, and next-generation communications.
4. References[1] H.-K. Wei et al. "Generation and manipulation of polarization-twisting dual pulses with a high degree of freedom," Opt. Lett. 45, 66636666 (2020)[2] H.-K. Wei et al. "Few-cycle THz wave manipulation with a high degree of freedom via f-t modulation," Opt. Lett. 48, 1016-1019 (2023)[3] Q. Chen et al. "Electro-optic transceivers for terahertz-wave applications," J. Opt. Soc. Am. B 18, 823-831 (2001).
[4] M. Sato et al. "Terahertz polarization pulse shaping with arbitrary field control," Nat. Photonics 7, 724–731 (2013).

NYCU-TUAT-UY Symposium

INV. 03

Energy transfer between Alq3 molecules and Si revealed by pump-probe spectroscopy
Yu-Chan Tai1, Wen-Yen Tzeng1,2, Jhen-Dong Lin1, Fu-Xiang Chen1, Yi-Hou Kuo1, Ruei-Jhe Tu1,
Ming-Yang Huang1, Shyh-Shii Pai3, Nick Weihan Chang3, Sheng-Yang Tseng3,
Chi Chen4, Chun-Liang Lin1, Shun-Jen Cheng1, Chih-Wei Luo1,5,6,7,8
1

Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 300, Taiwan .
2
Department of Electronic Engineering, National Formosa University, Yunlin 632, Taiwan.
3
FAB 12B, Taiwan Semiconductor Manufacturing Company, Ltd., Hsinchu 300, Taiwan.
4
Research Center for Applied Sciences, Academia Sinica, Taipei, 115, Taiwan.
5
Institute of Physics and Center for Emergent Functional Matter Science, National Yang Ming Chiao Tung University, Hsinchu 300, Taiwan.
6
National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan.
7
Taiwan Consortium of Emergent Crystalline Materials (TCECM), National Science and Technology Council, Taiwan.
8
Department of Physics, University of Washington, Seattle, Washington 98195, USA.
brianyjtai1994.sc08@nycu.edu.tw; cwluoep@nycu.edu.tw

Abstract: We utilize ultrafast optical pump-probe spectroscopy to uncover energy transfer
mechanisms between Alq3 organic molecules and Si semiconductors. The 400-nm pump and 800nm probe spectra provide comprehensive insights into SiO 2-thickness-dependent carrier relaxation
across Si’s continuous band, while the 400-nm pump with broadband-probe spectra depict carrier
population relaxation at multiple energy positions in Si’s conduction band. The presence of Alq 3
distinctly influences Si recombination dynamics, underscoring their interplay. We ascribe Si’scarrier dynamics alterations to nonradiative energy transfer, comparing the mechanisms totheoretical dipole-dipole interactions.
OCIS codes: (320.7130) Ultrafast processes in condensed matter, including semiconductors; (320.7150) Ultrafast
spectroscopy.

Figure 1: The presence of an Alq3 thin film significantly influences the photoexcited ultrafast carrier dynamics of Si
compared to the intrinsic Si carrier dynamics represented by the solid line. Scatter plots in three sets illustrate how
Si's carrier dynamics are modulated based on SiO2 thickness. The inset image depicts the schematic structure of the
Alq3/SiO2/Si sample.

NYCU-TUAT-UY Symposium 2023 INV. 04

Ultrafast Time-resolved and Vibrational Dynamics of Nativeand nitrosylated (NO-) Cytochrome cYing Kuan Ko1, Atsushi Yabushita1,2 and Takayoshi Kobayashi1,2,3,4
1

Department of Electrophysics, National YangMing ChiaoTung University, Hsinchu, Taiwan
2
Research Institute for Engineering, Kanagawa University, Kanagawa, Japan
3
Brain Science Inspired Life Support Research Center, The University of Electro-Communications, Tokyo, Japan
4
Research Center for Water Frontier Science and Technology, Tokyo University of Science, Tokyo, Japan
kentko78@gmail.com

Abstract: Using a homemade sub-10 fs broadband NUV laser pulses system, the primary reaction
mechanism of native and nitrosylated cytochrome c (Cyt c) were elucidated for two redox forms offerric (oxidized) and ferrous (reduced) Cyt c by measuring their transient absorption (TA) spectra. The
TA traces measured in the broad probe wavelength region were analyzed by the global analysis method
to study the electronic dynamics. With the temporal resolution of 10 fs, we observed TA signal
modulation caused by the molecular vibration in the time domain, which can be used to calculate theinstantaneous frequency of the molecular vibration mode.
Introduction
Cytochrome c (Cyt c) is a widespread hemeprotein in mammals, which usually are found in inner mitochondrial
membrane of cells, which involves in a variety of important biological processes, such as a trigger of apoptosis, anenergy transfer of electron transport chain (ETC) and an antioxidant for the cell. The interaction with cardiolipin
maintains the normal operation of mitochondria. Cyt c is mainly composed of a porphyrin macrocycle and a central ion
in redox (ferric, Fe3+-Met80) and reduced (ferrous, Fe2+-Met80) form. Both two redox forms can transfer to each otherwhile involving the ET reactions. In apoptosis process of cells, nitrosylated (nitric oxide bind-) Cyt c plays an importantrole as a trigger regulates the release of Cyt c from mitochondria or increase of its peroxidase activity. These phenomena
are associated with the conformational change of heme, the center structure of Cyt c [1].
We used time-resolved spectroscopy to investigate the reaction dynamics and processes of native and nitrosylated
Cyt c in two redox forms [1]. The results reveal that photo-dissociation and recombination between central ion andconnected ligand, Fe2+-Met80 in ferrous Cyt c dominated the ultrafast dynamic after ultrafast pulse excitation (seeFig.1(a) and (c)). On the contrary, the dissociation did not occur in ferric form. In nitrosylated form, photo-dissociation
occurred both in two redox forms and the recombination of NO is more slowly compared with native ferrous Cyt c.
Furthermore, the results of the real-time analysis of vibrational dynamics reveal a swifter tendency for structural recovery
following NO dissociation in as compared to Met80. In conclusion, the binding and dissociation of NO dominates theheme conformational changes and ultrafast dynamics of NO-Cyt c complex (see Fig.1(b) and (d))

Fig. 1 The transient absorption (TA) spectrum of (a) native and (b) nitrosylated ferrous Cyt c, with the corresponding
spectrogram traces in (c) and (d) are calculated within the probe wavelength range of 430-440 nm, respectively.
References[1] Y.K Ko, “Primary Electronic and Vibrational Dynamics of Cytochrome c Observed by Sub-10 fs NUV Laser Pulses,” J. Phys. Chem. B 124, 8249–
8258 (2020)

NYCU-TUAT-UY Symposium 2023 INV. 05

The polarization control of coherent mid-infrared pulses
generated through the four-wave-mixing filamentation
1

Wei-Hong Huang1*, Yi-Ruei Sie1, Chih-Wei Luo1
Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan.
*
Author e-mail address: nc7410@gmail.com

Abstract: We demonstrated the polarization control of coherent mid-infrared (MIR) pulses
which were generated through the laser-induced two-color filamentation. By manipulating thepolarization of injected two-color pulses, the combined two-color laser fields will drive
ionized plasma to change the resultant polarization of MIR pulses.
1.

Introduction

The optical mid-infrared (MIR) regions have various crucial molecular vibrational mode, which can help
researchers to identify the chemical bonds and formations of molecules or crystals. Based on these topics, many
research groups are interesting to developing a coherent MIR light sources which had enormous potential totemporally resolve the dynamics of energy transfer between chemical bonds. There is a popular method togenerate coherent MIR pulses is to use nonlinear four-wave-mixing (FWM) processes trough ionizedfilamentation which was induced by the two-color laser fields [1,2]. Through the laser-induced air plasma
filament, we can have much more smooth dispersion curve in MIR region. Because of that, relatively easierphase matching condition can make ultra-broadband MIR available. In the same time, the low dispersive air
plasma and self-compression effect can keep the output MIR pulse well in Fourier transform limit, so the enduser does not need to fix the chirp effect of pulse before the applications.
Straightforwardly, we can easily control the polarization of injected pules and the resultant laser-induced
filamentation will be modified as the field of laser pulses. This experimental control is a common method andwidely used in two-color systems, especially for THz generation [3]. In addition, some groups had noted that thegenerated THz through two-color laser-induced filamentation has abnormal enhancement when the injected
two-color pulses were circularly polarized rather than linearly polarized [4,5].
2.

Results and discussions

In our work, we had found similar behaviors when the MIR pulses generated by switching to circularly
polarized two-color filamentation. As the Fig. 1 shown, different types of dual waveplates (DWPs) were
employed in our setup to separately control the polarization types of two-color pulses. Fig 1(c,d) showed that thecircularly polarized MIR pulses can be generated by DWPb, a QWPs at 800 nm, but a FWP at 400 nm. The
output power of MIR pulse was also enhanced, comparing with the typical waveplates, DWPa. In summary,according to manipulating the polarization of injected two-color pulses, the combined two-color fields of plasma
will drive ionized plasma to different direction, and the resultant dynamic of ions will create four-wave-mixing
MIR pulses along with the corresponding direction.

Fig. 1. The power of FWM MIR pulses after passing through a MIR polarizer. The angles of polar coordinates werecorresponded to the angle between MIR polarizer and input fundamental pulses. The distances of polar coordinate werewith respect to the normalized power of MIR pulses. φ was the angle between DWP and input fundamental pulses.

References[1] W.-H.Huang, Y.Zhao, S.Kusama, et al, Opt. Express 28, 36527 (2020).
[2] Y.Zhao, S.Kusama, Y.Furutani, et al, Nat. Commun. 13, 1077 (2022).
[3] Z.Zhang, Y.Chen, S.Cui, et al, Nat. Photonics 12, 554 (2018).
[4] Y.-Y.Tu, C.Meng, X.Sun, et al, J. Opt. Soc. Am. B 39, A83 (2022).
[5] Q.Song, X.Yuan, S.Hu, J.Huang et al, Opt. Express 29, 22659 (2021).

NYCU-TUAT-UY Symposium 2023

INV. 06

Hyperspectral imaging using sub-cycle mid-infrared
pulses generated through two-color filamentation
Takao Fuji
Laser Science Laboratory, Toyota Technological Institute, Nagoya 468-8511, Japanfuji@toyota-ti.ac.jp

Abstract: We have demonstrated hyperspectral imaging using sub-cycle mid-infrared pulses
generated through two-color filamentation. Up-conversion of the MIR pulse transmitted
through the sample at the image plane significantly improve the performance of the spectral
imaging.
Hyperspectral imaging integrates imaging and spectroscopy to characterize chemical distributions. The resulting
spectral image, a “data cube,” combines two spatial dimensions with one spectral dimension, offering fullspectrum insights from each pixel. The power of mid-infrared (MIR) hyperspectral technique lies in its ability toperform “chemical imaging” or “chemical mapping,” capturing the molecular composition of objects throughmolecular vibration. However, the efficacy of the MIR hyperspectral imaging is hampered by limited pixels andthe low signal-to-noise ratio of MIR detectors.
To overcome these challenges, the concept of up-conversion emerges as a promising strategy. By converting
MIR ultrashort pulses into visible or near-infrared light, detection using Si-based detectors becomes feasible,
greatly enhancing performance. Prior approaches focused the MIR beam into a nonlinear crystal to generateintense visible light through wavelength conversion at the Fourier plane [1]. However, this method necessitates
wavelength-dependent image calibration based on phase matching conditions, hindering efficiency.
In this invited talk, a novel MIR hyperspectral imaging technique based on sub-cycle MIR pulses [2] isintroduced. With broad bandwidth spanning functional group (1500–3000 cm−1) and fingerprint (500–1500 cm−1) regions, and intense intensity facilitating wavelength conversion at the image plane, thisconfiguration eliminates wavelength dependency in image size. Figure 1(a) illustrates the two imaging types
with up-conversion.
Generating sub-cycle MIR pulses (13.4 fs) utilizes four-wave mixing through two-color filamentation [3]. A~4.4 μm thick GaSe crystal positioned on the sample’s image plane interacts with the MIR pulse passing
through the sample and a chirped 800 nm pulse (1.8 ps). This interaction generates a sum frequency signal
subsequently captured by a silicon-based hyperspectral camera, producing hyperspectral images for analysis.
Our analytical prowess is validated through imaging and mapping of A. cepa bulb leaf epidermal cells. Cells
affixed to 200 μm CaF2 substrates reveal intricate structures illuminated by visible light (Fig. 1(b)), while
hyperspectral imaging (Fig. 1(c)) maps cell wall (red), cytoplasm (cyan), and nuclei (green) through MIR
spectral analysis. Significantly, nuclei distribution is exclusively visible in the MIR hyperspectral image,underscoring the method’s potential for precise cell analysis. This innovative approach broadens horizons foradvanced hyperspectral imaging, particularly in the realm of cellular exploration and characterization.

Fig. 1(a) Schematic of the two types of the imaging with upconversion. (b) Microscopy image illuminated by visible light. (c) Mapped
hyperspectral images of the onion (A. cepa) bulb leaves epidermal cells.
[1] S. Junaid, S. Chaitanya Kumar, M. Mathez, M. Hermes, N. Stone, N. Shepherd, M. Ebrahim-Zadeh, P. Tidemand-Lichtenberg, and C.
Pedersen, “Video-rate, mid-infrared hyperspectral upconversion imaging,” Optica 6, 702–708 (2019).
[2] Y. Zhao, S. Kusama, Y. Furutani, W.-H. Huang, C.-W. Luo, and T. Fuji, “High-speed scanless entire bandwidth mid-infrared chemical
imaging,” Nat. Commun. 14 3929 (2023).
[3] W.-H. Huang, Y. Zhao, S. Kusama, F. Kumaki, C.-W. Luo, and T. Fuji, “Generation of sub-half-cycle 10 μm pulses throughfilamentation at kilohertz repetition rates,” Opt. Express 28, 36527–36543 (2020).

NYCU-TUAT-UY Symposium 2023

INV. 07

Label-Free Imaging of Melanoma with Confocal
Photothermal Microscopy
Takayoshi Kobayashi
Advanced Ultrafast Laser Research Center and Brain Science Inspired Life Support Research Center, University of ElectroCommunications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585, Japan

Abstract: Label-free confocal photothermal (CPT) microscopy was utilized for the first timeto investigate malignancy in mouse skin cells. Laser diodes (LDs) with 405 nm or 488 nm
wavelengths were used as pumps, and a 638 nm LD was used as a probe for the CPT
microscope. A Grey Level Cooccurrence Matrix (GLCM) for texture analysis was applied to
the CPT images. Nine GLCM parameters were calculated with definite definitions for the
intracellular super-resolved CPT images, and the parameters.
1. Introduction
Malignant melanoma (MM) is one of the most common cancers worldwide. It has a favorable prognosis only if
the affected area is removed at an early stage. MM reportedly causes the large majority of skin cancer deaths
despite the fact that it accounts for <2% of skin cancer cases [1]. The incidence of MM has been increasing for>30 years and one of its most ominous characteristics is its high propensity to produce distant metastases,
because it can get disseminated throughout the body through lymphatic and hematogenous spread. For thisreason, early detection and treatment of MM are crucial life-saving measures [2]. Although dermoscopy is a
powerful diagnostic technique [3] and the ABCDE (abbreviation for asymmetrical shape, border, color,
diameter, and evolution) rule provides a guide to the identification of involved areas, pathological examinationis the gold standard for MM diagnosis. But diagnosis remains highly reliant on the skill level of the pathologist.
2. Results
We developed a photothermal microscope with resolution beyond diffraction limit. The textural structure of theimages of the mouse skin samples containing both nevus and MM cells taken with the PT imaging method wereanalyzed by GLCM. The nine parameters were calculated as shown below. The areas of imaging data wereanalyzed by the GLCM method, and the 8-bit level gray level intensity distribution of the PT signal was
obtained. Twelve images of 72 × 72 μm2 to multiple samples of excitation at 488 nm for both nevus and MM
samples were also obtained. The areas of imaging data were analyzed by this method, and the 8-bit level graylevel intensity distribution of the PT signal was analyzed using the GLCM analysis. There were total of 48
images with an area of 18 × 18 μm2 from both nevus and MM providing sufficient data of various parts of skin.
We found that a few of the nine GLCM parameters clearly showed the ability to discriminate between nevus andMM, and can hopefully be used as criteria for pathological diagnosis [4,5].
We then performed receiver operating characteristic (ROC) curve analysis based on fitted Gaussian curves
to the observed distribution. An ROC curve is commonly used to evaluate the diagnostic ability of a test. Whena threshold parameter used in the system classifying examinees into two groups, positive and negative for somefeatures, this curve is plotted as the sensitivity against the false positive ratio. The d parameter d = 10 provides
the best performance for all nine GLCM parameters in both cases pumped at 405 nm and pumped at 488 nm.
We plotted ROC curves for nine parameters based on the Gaussian curves. The area under the curve (AUC) is
an indicator of the diagnostic ability; >0.9, 0.7~0.9, and <0.7 correspond to high accuracy, moderate accuracy
and poor accuracy, respectively. Entropy, Contrast and Variance show high AUCs, namely 0.909, 0.905 and
0.897, respectively. These values indicate that those parameters provide highly accurate methods to distinguishnevus and MM cells. In the case of 488 nm excitation, the AUCs of Prominence, Variance and Shade are 0.812,
0.808 and 0.768, respectively, indicating not as good performance as 405 nm excitation [4,5].
3. References[1] American Cancer Society. Melanoma Skin Cancer Overview. 2015. Available online: https://www.cancer.org/cancer/melanoma-skincancer.html (accessed on 14 August 2018.
[2] Rigel, D.S.; Carucci, J.A. Malignant melanoma: Prevention, early detection, and treatment in the 21st century. CA Cancer J. Clin. 2000,
50, 215–36.
[3] Soyer, H.P.; Smolle, J.; Kerl, H.; Stetner, H. Early diagnosis of malignant melanoma by surface microscopy. Lancet 1987, 2, 803.
[4 ] Kobayashi T. et al. Resolution enhancement of pump-probe microscope with an inverse-annular filter, Photonics (MDPI) 2018,25, 271.
[5] Kobayashi T. Label-free three-dimensional imaging of melanoma with confocal microscopy: Differentiation between malignant andbenign tissue, Bioengineering. (MDPI),.2018, 5, 67.

NYCU-TUAT-UY Symposium 2023

INV. 08

Quantum Enhancement for strength of vibrational
coupling between an optical cavity and molecules
Fumiaki Matsuoka
Tokyo University of Agriculture and Technology,2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japanfu-matsuoka@go.tuat.ac.jp

Abstract: It has been shown that when the optical modes of the optical cavity and thevibrational modes of the molecules are strongly coupled, the chemical properties of themolecules is changed. Since the strength of vibrational coupling in molecular-cavity systems
is mainly determined by the number of molecules, it is difficult to reach the vibrational strong
coupling regime for solutes in the liquid phase with low concentration and for the gas phase.
In this presentation, we theoretically show that quantum vacuum squeezing has the potential
to reduce the number of molecules required for strong coupling conditions by about 1/2 to
1/10 under the realistic or the feasible squeezing condition.

When the energies of the optical cavity modes and the vibrational mode of the molecules are matched in the
optical cavity, these modes are coupled even if there are no external electromagnetic fields. In particular, thestrength of such vibrational coupling is enough strong for the decay rate of the excited state of the molecules andthe decay rate of the cavity, a coupling state called vibrational strong coupling (VSC) is formed [1-8]. Under the
VSC formation, molecules in behave differently than those in free space such as accelerating or deceleratingorganic chemical reactions [2, 3], and modifications of self-assembly [4], etc.
The realization of VSC for various molecules would be important to understand the fundamentals of phenomena
and to open new applications. However, since the strength of vibrational coupling in molecular-cavity systems is
mainly determined by the number of molecules (i.e. concentration), it is difficult to reach the VSC regime forsolutes in the liquid phase with low concentration and for the gas phase.
Here, we consider another approach to enhance the strength of the vibrational coupling. It has been theoreticallyshown that squeezing of quantum vacuum fluctuations in the cavity field can enhance the coupling strength
between the optical cavity field and the two-level system in the cavity [9-11], and such enhancement effect has
been experimentally demonstrated in a two trapped ion qubits system to realize quantum gates [12]. While only
a two-level system is considered in these demonstrations, it remains unclear whether such a squeezing effectworks in many-molecules-cavity coupling system.
In this presentation, we theoretically demonstrate that the number of molecules required for strong coupling
conditions can be reduced by quantum squeezing effect of the cavity vacuum field using the Hamiltonian of amany-molecules-cavity coupling system with rotating wave approximation known as the Tavis-Cummings
model [5-8]. By applying squeezing operation to this model, we obtain an effective coupling constant geff = (gN1/2 er) /2 where g is the coupling constant, N is the number of molecules and r is the amplitude of the squeezing.
In addition, we calculate that the quantum vacuum squeezing has the potential to reduce the number ofmolecules required for strong coupling conditions [5] by about 1/2 to 1/10 under the realistic or the feasible
squeezing condition [13] and using typical parameters [1, 5, 12].
[1] A. Shalabney, et al., Nature Commun., 6, 5981 (2015).
[2] K. Hirai and H. Uji-i, Chem. Lett. 50, 727-732 (2021).
[3] F. J. G.-Vidal, et al., Science 373, 178 (2021).
[4] K. Hirai, et al., Chem. Sci. 12, 11986–11994 (2021).
[5] M. S. Rider and W. L. Barnes, Contemp. Phys. 62 (4), 217-232 (2021).
[6] T. E. Li, et al., Annu. Rev. Phys. Chem. 73, 43-71 (2022).
[7] M. Ruggenthaler, et al., arXiv:2211.04241 [quant-ph] (2022).
[8] A. Mandal, et al., ChemRxiv [Preprint] (2022). doi: 10.26434/chemrxiv-2022-g9lr7[9] S. Zeytinoğlu, et al., Phys. Rev. X 7, 021041 (2017).
[10] W. Qin, et al., Phys. Rev. Lett. 120, 093601 (2018).
[11] C. Leroux, et al., Phys. Rev. Lett. 120, 093602 (2018).
[12] S. C. Burd, et al., Nat. Phys. 17, 898-902 (2021).
[13] C. Riek, et al., Nature 541, 376–379 (2017).

NYCU-TUAT-UY Symposium 2023 INV. 09

Monitoring the progression of virus infection in plants using
Raman spectroscopy and principal component analysis
Kaustav Das*, Fawzia Novianti, Ken Komatsu, Terumasa Ito and Kazuhiko Misawa
Tokyo University of Agriculture and Technology, 2-24-16 Nakacho, Koganei, Tokyo 184-8588, Japan
Corresponding author: kdas@go.tuat.ac.jp; +81 42 388 7106

Abstract: Severity of the plant diseases challenging the global food security. Advancement oftraditional agricultural technology has become necessary. Here, we present a study to monitor the
progression of virus infection in plants using Raman spectroscopy and principal component analysis.
Our results presented a gradual spread of infection starting from the low infection level.
1.

Introduction

The everlasting effects of contagious plant diseases are posing one of the biggest challenges to global food security
along with the increasing demand for food supply and drastic climate change. Among the plant diseases induced from
pathogen interaction, virus induced diseases are the most difficult to monitor since they are generally asymptomaticin the initial levels of infections. Conventional methods [1] such as serological and molecular methods are critical in
detecting later levels of infections when the infection has become widespread. Such methods lack in monitoring
different levels of infections, especially the earliest ones. To provide a proper diagnosis and point of care, monitoring
the spread of infections from low to high levels has become necessary. Now, Raman spectroscopy (RS) [2] which
provides molecular dynamics in a non-invasive and non-destructive manner, becomes beneficial for obtaining acute
spectral signatures related to different levels of infection. Therefore, we present a model study for monitoring the
progression of virus infection using RS and principal component analysis (PCA). We used two sets of plants, one
being non-infected or healthy set and the other being infected set. Spectra were acquired between 6 to 12 dpi (dayspost inoculation). By comparing the results (PC score plots) between healthy and infected samples, a gradualcharacteristic difference was obtained in each dpi with 12dpi being the most distinctive. Such gradual differences
between healthy and infected samples led to monitoring the progression of infection in a systematic manner.
2.

Methods

We used Arabidopsis thaliana plants for this study. The infected set of such plants
were inoculated with plantago asiatica mosaic virus. The infected and healthy set ofplants were measured using a self-made confocal spontaneous Raman microscope on
6, 9 and 12 dpi. The measured spectra were preprocessed for baseline adjustment andthen subjected to PCA. PCA converts the highly correlated variables of spectral data
into few uncorrelated variables with maximum variance termed as principal
components (PC). Score of such PCs can represent trends between spectral datasets.
3.

Results and discussion

Figure 1 shows the PC score plots for healthy and infected samples. PC scores of eachdpi presents their individual grouping with group-separation getting larger after 9 dpi.
Although both healthy and infected samples exhibited similar trends for each groupof PC scores, they seem to differ characteristically when compared directly among
the healthy and infected samples. Such difference is relatively smaller in the 6 and 9dpi, while 12 dpi shows the largest difference. These characteristic differences
between healthy and infected samples convey the spreading of infection. Thus, themodel study was able to monitor the progression of virus infection, starting from low
to high level of infection. Although we were successful in monitoring the spread ofvirus infection, to detect the presence of virus at the earliest accurately, more robust
experimental protocol will be implemented in the future.
4.

References[1] F. Martinelli et. al., Agron. Sus. Dev. 35, 2015.
[2] C. Farber and D. Kurouski, Anal. Chem. 90, 2018.

NYCU-TUAT-UY Symposium 2023

INV. 10Terahertz Emission from Topological Material
SrCd2Sb2 single crystals
Po-Wei Gong1, Yi-Cheng Cheng1, Pei-Tsung Yang1, Xin-Yun Chang1, Jiun-Haw Chu2,
Cheng-Chien Chen3, Jiunn-Yuan Lin4, Chih-Wei Luo1, and Chien-Ming Tu1*
1

Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 300093 Taiwan
2
Department of Physics, University of Washington, Seattle, WA, 98195 USA
3
Department of Physics, University of Alabama at Birmingham, Birmingham, AL, 35294 USA
4Institute of Physics, National Yang Ming Chiao Tung University, Hsinchu, 300093 Taiwan
e-mail address: cmtu@nycu.edu.tw

Abstract: We report on terahertz emission from topological material SrCd 2Sb2 single crystals
under ultrafast optical excitation with different polarization. Nonzero circular dichroism of theemitted THz radiation were observed as the polarization of optical pulses switch from rightcircular polarization to left circular polarization. The observed phenomena are coincident withcircular photogalvanic effect. Our work demonstrates the potential applications of SrCd2Sb2
on opto-spintronics devices.
Introduction
Topological materials (TMs) have attracted much interests both theoretically and experimentally due to their
exotic transport phenomena, and potential applications in spintronics. Dirac and Weyl semimetal are quantum
matters which its conduction and valance bands cross each other and show linear dispersion around pairs of
nodes in reciprocal space. Magnetic Weyl semimetal is bearing seeking for long time, and EuCd 2Sb2 has been
predicted as an ideal magnetic Weyl semimetal. SrCd2Sb2, the non-magnetic analogue of EuCd2Sb2, has also
been predicted to show non-trivial topological phase in room temperature. Besides, THz emission spectroscopy
is a powerful contact-free tool to detect the dynamics of photocurrents in topological materials through circular
photogalvanic effect [1, 2]. In this study, we report on terahertz emission spectroscopy of SrCd2Sb2 single
crystals. Significant nonzero circular dichroism of terahertz emission were observed, and this phenomenon
agrees with circular photogalvanic effect originated from topological states well.
Results

Figure 1. a, circularly polarized optical pulses illuminated a SrCd 2Sb2 single crystal at an oblique angle θ = 45o of incidence to generate
photocurrents (JTHz) with direction perpendicular to the plane of incidence. In b-d, the figures show the emitted THz radiation at different
sample orientation of ϕ = 0°, 45° and 90° respectively. α : the phase angle of the quarter-wave plate (QWP). The colors represent thepolarization of optical pulses: linear- (blue), right-hand-circular- (cyan) and left-hand-circular-polarization (red) for α = 0°, 45°, 135°
respectively.

Figure 1 shows the THz waveforms excited by femtosecond optical pulses of different polarization at different
sample orientations ϕ. S-wave THz radiation was detected. In-plane contributions to the THz radiation are
included only, and the contributions from bulk can be excluded in this scheme. At ϕ = 0°, as shown in Fig. 1b,
significant THz emission was observed under linear polarized (quarter wave-plate phase angle α = 0°) opticalexcitation. As the polarization of optical pulses changed to right-/left-circular polarization (α = 45°/135°),
similar THz wave-forms were observed, and the polarity of the THz wave did not change also. However,nonzero THz emission circular dichroism can be observed. Interestingly, the polarity of the all THz emission
circular dichroism show the same polarity, and it indicates the spin-polarized photocurrents keep their direction
under the rotation of samples along sample’s surface normal. These phenomena are coincident with circular
photogalvanic effect-the spin-polarized photocurrent originated from topological states of TMs.
[1] N. Sirica, et al., “Tracking Ultrafast Photocurrents in the Weyl Semimetal TaAs Using THz Emission Spectroscopy,” Phys. Rev. Lett. 22,
197401 (2019).
[2] L. Luo, et al., “A light-induced phononic symmetry switch and giant dissipationless topological photocurrent in ZrTe5,” Nat. Mat. 20,
329, (2021).

NYCU-TUAT-UY Symposium 2023

INV. 11

Initial reaction dynamics of a red fluorescent protein TagRFP under mutation of
S158T observed by 10fs visible laser pulse
A

National Yang-Ming Chiao-Tung Univ., BKanagawa Univ., CJILA-University ofColorado Boulder
Atsushi YabushitaA,B，QiuJun LinA，Ying Kuan KoA，Takayoshi KobayashiA,
Izumi IwakuraB, Ralph JimenezC
In the field of bioimaging, fluorescent proteins (FPs) emitting different colors areused to observe various components in a single shot taking the image in full color.
TagRFP is one of FPs emitting red color whose photostability is known to be improvedby mutation of S158T [1]. The improvement is thought to be related with a reactivation
process which only appears in the mutant [2], however its mechanism is still not clear.
We have observed ultrafast dynamics of the original TagRFP and its mutant tovisualize the difference in their primary photoreaction. The pulse duration of the 10fs
visible pulse laser could visualize the vibrational dynamics simultaneously observing
electronic dynamics. The mechanism which causes the difference was well explainedby comparing the result with quantum chemical calculation.

Fig. 1 (Left) Two dimensional view of the measured transient absorption spectra and (Right)
Calculated vibrational mode corresponding to the difference appearing on mutation.
[1] Nathan C Shaner, Michael Z Lin, Michael R McKeown, Paul A Steinbach, Kristin L Hazelwood,
Michael W Davidson & Roger Y Tsien, “Improving the photostability of bright monomeric orange
and red fluorescent proteins”, Nature Methods, 5, 545-551 (2008)[2] Rui Liu, Qing-Nan Liang, Shu-Qi Du, Xiao-Jian Hu, Yu Ding, “The crystal structure of red
fluorescent protein TagRFP-T reveals the mechanism of its superior photostability”, Biochem
Biophys Res. Commun., 477 (2):229-234 (2016)

NYCU-TUAT-UY Symposium 2023

INV. 12

Nematic ultrafast dynamics in SnS crystals
Nguyen Nhat Quyen1, Tz-Ju Hong1, Chin En Hsu2, Wen-Yen Tzeng1, Chien-Ming Tu1, Chia-Nung Kuo3,4,
Hung-Chung Hsueh2,5, Chin-San Lue3,4, Chih-Wei Luo1,4,6,7
1

Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
2
Department of Physics, Tamkang University, New Taipei City 251301, Taiwan
3
Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan
4
Taiwan Consortium of Emergent Crystalline Materials, Ministry of Science and Technology, Taipei 10601, Taiwan
5
Research Center of X-ray Science, College of Science, Tamkang University, New Taipei City 251301, Taiwan
6
National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan
7
Institute of Physics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan

Abstract: This study determines the nematic ultrafast dynamics of photoexcited electrons andphonons in SnS single crystals using polarization-dependent femtosecond spectroscopy at
various temperatures. Besides the fast relaxation of photoexcited electrons, a damped
oscillation component with a frequency of 36~41 GHz is also present in transient reflectivity
change (∆R/R) spectra generated by the thermoelastic effect. The results of this study showthat electrons and coherent acoustic phonons demonstrate significant anisotropy on the acplane in the transition region from 330 K to 430 K, possibly because of strong electronphonon coupling. These are essential in anisotropic heat dissipation and charge carrier
mobility in polarization-sensitive optical and optoelectronic devices.
1. Introduction
New classes of two-dimensional (2D) materials beyond graphenes, such as transition metal dichalcogenides(TMDCs) and black phosphorus, have significant physical/chemical properties and many potential applications.
Since the highly symmetrical crystal structure, graphene and most TMDCs feature in-plane isotropic
characteristics. However, some 2D materials, such as black phosphorus and the bulk orthorhombic group IV-VI
compounds of SnS, SnSe, GeS, and GeSe, exhibit significant in-plane anisotropic properties and have a low
lattice symmetry. Similarly to black phosphorus, SnS is a layered material with anisotropic electronic properties
and good environmental, thermal, and dynamic stability. However, there is no study on the ultrafast dynamic
responses and acoustic phonons in SnS, particularly the evolution of electronic and phononic anisotropies.
2. Results and discussion
Figure 1(a) shows the crystal structure of SnS and schematics of the polarized pump-probe measurements [1].
The grey and yellow balls represent Sn and S atoms, respectively. The ∆R/R was measured using a dual-color
pump-probe system (400 nm/3.1 eV pump, 800 nm/1.55 eV probe) and the standard lock-in technique with afemtosecond Ti:sapphire laser as the light source for the excitation pulses (a pulse duration of 70 fs and arepetition rate of 5.2 MHz). The respective fluences of the pump and probe beams were 73.2 J/cm-2 and 5.5
J/cm-2. As shown by Fig. 1(b), the typical ∆R/R along the a-axis of SnS at 300 K with the fitting of an ∆R/R=
… Eq. (1). The solid line is the sum of the dashed lines. The inset shows theoscillation component of ∆R/R when the decaying background is subtracted, and the curve is fitted using acosine function (solid line). Fig. 1(c) shows the orientation-dependent ∆R/R for an SnS single crystal, from θprobe= 0° (zigzag direction) to 90 (armchair direction) at 300 K. The results of this study show that electrons andcoherent acoustic phonons demonstrate significant anisotropy on the ac-plane. For the details of this study,
please refer to Ref. [1].

Fig. 1. The nematic dynamics of photoexcited electrons and phonons in SnS single crystals are revealed using polarization-dependent
femtosecond spectroscopy.

3. References[1] Nguyen Nhat Quyen et al., “Nematic electron and phonon dynamics in SnS crystals,” App. Phys. Lett. 121, 172105 (2022).

NYCU-TUAT-UY Symposium 2023

ORG. 01

Recording and batch decoding of SQAM signal
for Holographic memory
Satoshi Honma, Hironori Ito,
University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi, 400-8511, Japan
shonma@yamanashi.ac.jp

Abstract: Recording scheme of a spatial quadrature amplitude modulated (SQAM) signal is
expected to improve the recording density of the holographic data storage (HDS). The problem
is to realize this with simple optics. In this report, we explain our concept of the interleaved
phase method to generate the SQAM signal and of the batch decoding technique of the
reproduced signal with simple optical constructions.
1. Introduction
It is expected that HDS will be developed as the next generation optical memory. A recording scheme of a SQAM
signal is a promising technique to achieve high recording density of the HDS. It is important to design a simple
optical system for the generation of the SQAM signal and the phase measurement of the reproduced signal. We
have proposed the interleaved phase method to generate the SQAM signal with a spatial phase modulator. We arealso currently investigating a phase detection method by simultaneously reproducing of SQAM signals using HDS
optics as an optical interferometer. We introduce the concept of the systems. Spatial Phase modulator
2. Interleaved phase method for generation of SQAM signal
Fig. 1 shows the recording process of the SQAM signal in the HDS with theinterleaved phase method. To generate the SQAM signal of 𝐴𝑥,𝑦 exp 𝑗𝜑𝑥,𝑦 ,we calculate the phase distribution for the spatial phase modulator given by𝜃𝑛,𝑚 = 𝜑𝑥,𝑦 + (−1)𝑛+𝑚 acos(1 − 𝐴𝑥,𝑦 )Lens
Reference beam

(1)

, where 𝜑𝑥,𝑦 and 𝐴𝑥,𝑦 are phase and amplitude of the SQAM signal atcoordinates (𝑥, 𝑦) of the symbol, 𝑛 , 𝑚 are the horizontal and vertical
pixel coordinates of the spatial phase modulator. 𝑐 × 𝑐 pixels are used torepresent one symbol of the SQAM signal, where in general 𝑐 is generally
8. The phase-modulated light, whose phase value is 𝜃𝑛,𝑚 by the spatial
modulator, is passed through the spatial low-frequency filter optics to remove
unwanted components, resulting in the final SQAM signal of 𝐴𝑥,𝑦 exp 𝑗𝜑𝑥,𝑦 .
3.

Bath reading and decoding (BRD) of SQAM signal

Spatial filter

Holographic disc

Fig. 1 Recording process
Camera device

Lens
SQAM signals

Reading beams

Fig. 2 Batch reading process
Fig. 2 shows the conceptual diagram of the BRD. Three SQAM signals are
simultaneously reproduced from holograms recorded at different positions
by irradiating multiple reading beams. Since the signal beams are incident to the camera at different angles,
interference fringe patterns with multiple different spatial frequencies are formed according to the angulardifference between the beams. The complex amplitude distributions of the 𝑖-th SQAM signals is defined by 𝐶𝑖 =𝐴𝑖 exp 𝑗𝜑𝑖 (𝑖 = 0, 1, 2). From the spatial frequency difference, the distribution corresponding to 𝐶1 𝐶0∗ and 𝐶2 𝐶0∗
can be extracted using Fourier analysis, where the asterisk indicates the conjugated phase. Assuming that only
SQAM signal distribution 𝐶0 is known in advance, by dividing 𝐶0∗ from the above distribution, the distributions
𝐶1 and 𝐶2 can be decoded. Fig. 3 shows the analytical result of the decoded signals by BRD. The decoding is
confirmed to be relatively accurate, although distortions occur near the pixel boundaries.
4.

Conclusion

2

We have presented our proposed method ofrecording an SQAM signal in a holographic memoryand decoding the complex amplitude value of the
reproduced signal using a simple optical system.
5.

References

Quadrature
phase

In
Phaes

amplitude

phase

0

Constellation map[1] S. Honma, T. Sekiguchi, “Multilevel phase and amplitudeFig. 3 Decoded SQAM signal
modulation method for holographic memories with programmablephase modulator”, Opt. Rev. Vol. 21, pp. 597–598 (2014)[2] J. Igarashi, H. Ito, S. Honma, “Batch recording of multiple SQAM signal and self‑reference detection technique”, Opt. Rev., online (2023).

NYCU-TUAT-UY Symposium 2023

ORG. 02

Pulse shaping for 3-dimentional integrationof kinetic energy via light
Hironori Ito, Yuki Uchiyama and Satoshi Honma
University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi, 400-8511, Japan
hito@yamanashi.ac.jp

Abstract: This study is to challenge how efficiently pulse shapes can be used to convert
kinetic energy into liquid kinetic energy. This is fundamental study of pulse shaping to matchthe temporally changing solvent state to achieve the minimum entropy state that generates the
maximum amount of work. The energy dense state of the liquid is converted into fluid kinetic
energy through cycles of bubble formation and contraction. Introduce a new concept of 3dimentional integration of kinetic energy to fields such as biomedicine and robotics byimproving the efficiency of light-kinetic energy conversion and expanding its applicability.
1. Introduction
The generation of bubbles by irradiating a liquid with a femtosecond pulsed laser (fs laser) has attracted
attention as a phenomenon for distributing kinetic energy with high spatial resolution on the micrometer scale.
[1,2] Even though the fundamental wave is not absorbed in water, at the fs laser focal point, the generation andcontraction of bubbles is accompanied by the generation of plasma due to multi-photon absorption. The bubble
expansion-contraction cycle powers fluid pumping and actuators. Especially in microfluidic devices, where
wiring is considered difficult, distributing optical energy to any desired position in three-dimensional spaceenables systematic operation of integrated power sources, as shown in Fig. 1. Despite the strong desire for sucha prospect, current research on laser-induced bubbles is focused on processing and analysis and lacks a measureof optical-kinetic energy conversion efficiency.
2. Plan to improve energy conversion efficiency with pulse shaping
For minimum entropy, as many photons as possible must be used to excite electrons in a limited space. The
pulse waveform is optimized based on the density of the electronic state of the liquid and the wavefront at the
focal point. In order to clarify the achievement of kinetic energy conversion of liquid by pulse shape, (1) an
observation system for bubbles generated by laser will be constructed, and (2) the kinetic energy is evaluatedfrom the flow velocity of the liquid and feedback is provided to the parameters of pulse shape.
Operation of micro
soft actuators

AcetonePumping by bubbles
in capillary channels

Jet

Grass wall
BubbleFocal point
Spectroscopy
by the samelight source

500 mFig. 1 Systematic applications realized by 3D kineticenergy integration by light such as microfluidic devices

Fig. 2 CMOS Image of micro
jet from laser induced bubbles

3. Preliminary experiments on bubble generation by laser
The optical cell was filled with acetone and a femtosecond laser pulse was focused on the methyl-elo deposit on
the wall surface. A strong microjet was observed with the generation of bubbles as shown in Fig. 2. Thisphenomenon is known to be caused by the Marangoni effect due to the temperature gradient at the gas-liquidinterface and the expansion and contraction cycle of bubbles. This jet enables visualization of momentum,
which can be used to evaluate energy conversion efficiency.
4. Conclusion
Improvement of optical-kinetic energy conversion efficiency by pulse shaping is proposed. This research willlead to medical and industrial applications through three-dimensional integration of kinetic energy using light.
5. References[1] Y. Tagawa et.al., Physical Review X 2 031002 (2012).

[2] Y. Hosono et.al., JJSP 84 11 (2018).

NYCU-TUAT-UY Symposium 2023

POS. 01

Detection of structural changes in DNA due tomethylation using Raman spectroscopy
Haruki Kanae and Kazuhiko Misawa

Department of Biomedical Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo, Japan
Author e-mail address: s233092t@st.go.tuat.ac.jp

Abstract: DNA methylation regulates transcription, and its aberration is one of the causes ofcancer. Previous studies have suggested that DNA methylation has some effect on DNA
conformational changes. However, detailed structural information has not been obtained. In
this study, we investigated the structural changes in DNA caused by methylation using
Raman spectroscopy (RS).
1. Introduction
Cancer is one of the common causes of death in the world. If the detection of it gets delayed,
the rate of survival decreases and the burden of treatment increases. Therefore, early detection isessential. Loss of normal transcriptional regulation by abnormal deoxyribonucleic acid (DNA)causes cancer. General cancer detection techniques include imaging and tumor marker; however,these methods can only detect cancer after it has progressed to a certain stage. For earlier detection,
it is required to accurately detect DNA abnormalities that led to cancer.
DNA methylation is one of the mechanisms that regulate DNA transcription and suchabnormalities have already been identified in many cancer patients. However, it is not clear how
DNA methylation affects transcriptional regulation. Tsukakoshi et al. [1] demonstrated that thebinding activity of DNA oligonucleotides derived from gene promoter regions to a transcription
factor is altered by methylation. This suggested that the conformational change caused bymethylation may affect transcriptional regulation. In the previous works, circular dichroism (CD)
spectra were measured to analyze the effects of methylation on the DNA structures, however, CD
does not provide detailed structural information.
In this study we use Raman spectroscopy (RS) to detect conformational changes in DNA
induced by methylation. Since RS generates vibrational information of molecules, it allows us to
identify structural modifications of DNAs [2]. With this method, we elucidate the transcriptional
regulatory mechanism of DNA methylation by investigating how structural differences
determined by RS affect transcriptional regulation.
2. Method
To observe the structural changes caused by methylation, Raman measurements were performed
on DNA differing only in the presence or absence of methylation. The samples measured were
methylated and unmethylated Hras1. Hras1 is an oncogene that produces the RAS protein, whichis responsible for intracellular signaling that promotes cell multiplication.
3. Results and Discussion
Figure 1 shows the Raman spectra of methylated and unmethylated Hras1. These differences inspectra reflect only differences due to methyl groups and differences in DNA structure. The
spectra confirmed the spectral changes associated with the conformational changes of DNA. In
the future, we will investigate how the conformational differences affect transcriptional regulation
to elucidate the transcriptional regulatory mechanism of DNA methylation.
References[1] K. Tsukakoshi, S. Saito, W. Yoshida, S. Goto, K.
Ikebukuro, “CpG Methylation Changes G-Quadruplex
Structures Derived from Gene Promoters and Interaction
with VEGF and SP1,” Molecules 23, 944 (2018).
[2] J. Palacký, P. Mojzeš, I. Kejnovská, M. Vorlíčková, “Does
Raman spectroscopy recognize different G-quadruplex
arrangements?” J. Raman Spectrosc. 51, 301–312 (2020).

Fig.1 Raman spectra of methylated and unmethylated Hras1

NYCU-TUAT-UY Symposium 2023

POS. 02

Toward Discovery of Biomarkers for New Diagnostic
Techniques of IgA Nephropathy
Daichi Igarashi, Terumasa Ito, Daisuke Yoshino, and Kazuhiko Misawa
Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japans231086s@st.go.tuat.ac.jp

Abstract: Kidney biopsy is used for definitive diagnosis of IgA nephropathy, but its invasivenature is a challenge. Although minimally invasive diagnostic techniques have beendeveloped, none of them have been put into practical use. This study aims to create a kidneymodel that can reproduce IgA nephropathy, which is necessary for the discovery ofbiomarkers that can lead to the development of minimally invasive diagnostic techniques.
Introduction
The kidneys have a filtration function by excreting and reabsorbing substances in the body. IgA nephropathy is
one of the intractable diseases and may progress to kidney failure. In this disease, IgA, one of the immune
antibodies, becomes abnormal for some reason and deposits in kidney cells. This leads to inflammation of theglomerulus and impairs the filtration function [1].
In Japan, kidney biopsy, in which kidney tissue is collected, is currently used for definitive diagnosis, but it
is highly invasive and places a heavy burden on patients. A minimally invasive diagnostic method using Gd-IgA,
one of the abnormal IgA, as a biomarker and measuring its amount in the patient's serum was developed [2].
However, because healthy individuals likely to have Gd-IgA and the amount of Gd-IgA varies amongindividuals, it is difficult to distinguish between healthy individuals and patients; thus, the accuracy of diagnosis
is low.
This study aims to help researchers search for biomarkers that specifically occur after glomerular
inflammation to develop new diagnostic techniques to distinguish IgA nephropathy patients from healthy
controls in a minimally invasive manner. However, in general, the search for biomarkers requires the use of
biological samples such as tissue or blood derived from patients. In such studies, it is also necessary to
manipulate the presence or absence of inflammation and make comparisons. Recently, attention has been
focused on modeling kidney disease using kidney organoids. In this work, as the first step, we create a kidneymodel that can reproduce IgA nephropathy.
The experimental plan toward the creation of a kidney model is outlined as follows. To reproduce thepathogenesis principle of IgA nephropathy as described above, the kidney model uses co-culturing of bothkidney cells and glomerular models. In addition, it is necessary for the model to reproduce the inflammation thatis caused by aberrant IgA. Therefore, we first test multimeric IgA, a type of aberrant IgA, to check whether it
can cause inflammation. The kidney cells are cultured in the medium mixed with the multimeric IgA todetermine the presence or absence of cellular inflammation. Once the inflammation is confirmed, we plan tocreate a more realistic kidney model with co-culturing of kidney cells together with a glomerular model, where
the presence or absence of inflammation is again determined. Finally, we will also examine whether the tissue
degeneration characteristic of IgA nephropathy is reproduced.
Currently, using kidney cells cultured in medium mixed with multimeric IgA, we are testing
immunofluorescent antibody methods to confirm whether multimeric IgA is deposited on the cells and to
confirm the distribution of the deposited multimeric IgA. In this presentation, I will talk about the current
progress of the experiment.

References[1] Suzuki, Hitoshi, et al., "The pathophysiology of IgA nephropathy," Journal of the American Society of Nephrology 22, 10, 1795 (2011).
[2] Bagchi, Soumita, et al. "Significance of serum galactose deficient IgA1 as a potential biomarker for IgA nephropathy: A case control
study," PLoS One 14, 3, e0214256 (2019).

NYCU-TUAT-UY Symposium 2023

POS. 03

Suppression of the Tailing Effect for Pathogen
Inactivation with UVC Ultrashort Pulsed Light
Shundai YamamotoA, Hideki AbeB and Kazuhiko MisawaA
Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo, JapanA
Research and Development Department, Central Blood Institute, Japanese Red Cross Society, Tatsumi 2-1-67, Koto-ku, Tokyo, JapanB
Author e-mail address: s226963q@st.go.tuat.ac.jp

Abstract: In the inactivation of pathogens by ultraviolet light, the inactivation rate has beenreported to decrease with increasing irradiation dose, which is commonly known as the tailing
effect (TE). In this study, we compared the inactivation effects between CW-LED andfemtosecond pulsed laser for developing a new method to suppress TE. We found that
femtosecond pulsed lasers suppressed TE and inactivated pathogens by more than one order ofmagnitude in comparison with CW-LED. The results of this study provide a new method forthe practical application of bacterial inactivation by ultraviolet light.
1. Introduction
The spread of contagious infections has increased the demand for technologies to inactivate pathogens by
ultraviolet (UV) irradiation. UVC (200-280nm) light inactivates pathogens by denaturing the nucleic acids bydirect absorption, without the aid of chemical components. The inactivation kinetics of UV light follows
logarithmic decay model if the inactivation rate is constant. However, experimentally, the assumption of aconstant inactivation rate breaks down. Previous studies have shown that the inactivation rate decreases withincreasing irradiation dose, which is commonly known as the tailing effect (TE). One such study reported that
TE occurs under UV inactivation in phosphate buffer solution (PBS) with pathogen aggregation and suggested
that TE may originate from light shielding effects and/or photo-reactivation [1]. Despite the advances inunderstanding the mechanism, there are few reports on how to suppress TE. In this study, we propose a newirradiation method using ultrashort pulsed light (UPL) in the UVC region to suppress TE. A CW-LED and a
femtosecond (fs) pulsed laser were irradiated to bacterial solution, and their survival rates were compared.
2. Methods
E. coli (NBRC 3301) was suspended in PBS and the viable bacteria concentration of the bacterial solution was
adjusted to 108 CFU /mL (CFU: colony forming unit). 100 µL of the suspension was then sealed in a 1 mm
optical path length quartz cell with a magnetic stirrer. An LED with a center wavelength of 268 nm and aspectral width of 11 nm was used as the continuous light source. The pulse source was a fs pulsed laser with acenter wavelength of 800 nm, repetition rate of 10 kHz, pulse energy of 0.5mJ and pulse width of 40 fs. The
light was then converted to pulsed light with a center wavelength of 268 nm and a spectral width of 2.1 nm
using third harmonic generation. Peak power of fs pulse had approximately 8 orders of magnitude higher thanthat of LED. As the fs pulsed laser has a Gaussian spatial intensity distribution, a diffuser was installed in frontof the irradiated sample to ensure a uniform intensity distribution on the irradiated surface. Also, a 10 mm
square aperture mask was placed in front of the sample for both lights. The irradiation dose was calculated as
the product of average power and irradiation time; the average power was set to be at 1.0 mW/cm2 for bothlights. The bacterial inactivation effect was assessed using bacterial survival counts by microscopic observation.
All samples were diluted in PBS, applied to LB agar medium and incubated at 35°C for 24 hours. The bacterial
survival rate was calculated from dividing the number ofbacterial colonies before and after light irradiation.
3. Results and Discussion
The results of the bacterial inactivation effects are shownin Fig. 1. We found that the CW-LED exhibited TE andproduced inactivation less than 4 orders of magnitude at
700 mJ/cm2, whereas the UPL suppressed TE andinactivated the pathogen over 5 orders of magnitude at
the same irradiation dose. We are currently carrying out
microscopic observations to examine the formation ofpathogen aggregation under continuous and pulsed lightirradiation.
Reference:[1] Eirini Vitzilaiou, Asaph M. Kuria, Henrik Siegumfeldt, Morten A.
Rasmussen, Susanne Knøchel, The impact of bacterial cell aggregation
on UV inactivation kinetics, Water Research 204, 117593 (2021).

Fig. 1. UV irradiation dose response of E. coli inactivated bypulsed laser and CW-LED

NYCU-TUAT-UY Symposium 2023

POS. 04

Acquisition of Raman Spectra of Foamed Macrophages
for Early Diagnosis of Atherosclerosis
Kohei Eguchi*, Terumasa Ito, Daisuke Yoshino and Kazuhiko Misawa
Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan*s234206t@st.go.tuat.ac.jp

Abstract: Current diagnosis of atherosclerosis is made after plaque formation, which canlead to vascular disease. In this study, we will use Raman microscopy to investigate
substances that may serve as markers for early diagnosis of atherosclerosis in macrophage
foam formation, foam cell accumulation, and plaque formation.
Arteriosclerosis is a general term for a disease in which plaque and thrombi form on arterial walls due to thedeposition of cholesterol and other substances, resulting in hardening and loss of elasticity of the arterial walls,
making blood vessels more likely to become clogged. In particular, atherosclerosis is the most common form ofarteriosclerosis, and diseases such as myocardial infarction, angina pectoris, and stroke associated withatherosclerosis are the leading causes of death worldwide [1].
Plaques in atherosclerosis are formed as shown in Figure 1. First, low density lipoprotein (LDL), a type ofcholesterol, enters the vascular endothelium from the artery and is oxidized ((1) in Fig. 1). Then, macrophages
in the vascular endothelium take up the oxidized LDL ((2) in Fig. 1) and form foam cells filled with lipid
droplets ((3) in Fig. 1). When foam cells accumulate, they form plaques ((4) in Fig. 1). When this plaqueruptures, deposits within the plaque leak into the bloodstream, causing thrombus formation and vascularocclusion, which may induce myocardial infarction or angina pectoris [2]. Currently, the most common
diagnostic methods for atherosclerosis are MRI and CT angiography to examine the narrowing of blood vessels
and changes in blood flow caused by plaques formed on the arterial wall. These tests can diagnose plaques witha particularly high risk of rupture, but these methods cannot be used unless the plaques are formed to an
observable size. Therefore, it is important to establish a technique to observe the early stages of macrophage
accumulation (i.e. early stages of plaque formation) for early diagnosis of atherosclerosis.
Stiebing et al. observed the uptake of oxidized LDL by macrophages using Raman spectroscopy, which isparticularly easy to discriminate lipids due to differences in molecular vibration [3]. As a result, they found
Raman bands of β-carotene specific to the lipid portion of macrophages that took up oxidized LDL. However,the detection of β-carotene does not indicate macrophage foaming. Early diagnosis of atherosclerosis requires
direct detection of changes in components and molecular structures involved in foam cell formation andaccumulation that lead to plaque formation.
In this study, we propose to use Raman spectroscopy to investigate not only the uptake of oxidized LDL bymacrophages, but also possible markers of atherosclerosis in macrophage foaminess, foam cell accumulation,and plaque formation for early diagnosis of atherosclerosis. As the first step, LDL is oxidized and thenincubated with macrophages to allow the macrophages to take up the oxidized LDL, and spontaneous Raman
microscopy is used to observe whether the macrophages have taken up the oxidized LDL and whether themacrophages are bubbled. This presentation will describe the experimental technique in detail and the progressof the study.

Figure 1. Schematic representation of the progression of the atherosclerosis[1]World Health Organization, “Cardiovascular diseases”, 2021.
[2]Ross R, “The pathogenesis of atherosclerosis: a perspective for the 1990s”, Nature, 29;362(6423), pp.801-809(2003).
[3]Clara Stiebing, et.al, “Raman imaging of macrophages incubated with triglyceride-enriched oxLDL visualizes translocation of lipids
between endocytic vesicles and lipid droplets”, JOURNAL OF LIPID RESEARCH, Vol. 58, Issue 5, pp.876-883(2017).

NYCU-TUAT-UY Symposium 2023

POS. 05

Transdermal Penetration of Self-Dissolving Microneedles
Using Coherent Raman Scattering Microscopy
Yuki Sekiya and Terumasa Ito
Department of Biomedical Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo, Japan
Author e-mail address: s208239q@st.go.tuat.ac.jp

Abstract: Self-dissolving microneedles hold promise as a novel drug delivery approach.
However, conventional analytical approaches lack the ability to measure real-time drug
penetration through the skin. We present a transdermal penetration measurement of lowmolecular-weight drugs in dissolvable microneedles using coherent Raman scattering
microscopy. This non-labeled and real-time drug measurement will contribute significantly
towards evaluating the effectiveness of medical MNs and advancing their practical use.

The epidermis possesses a barrier function against water and external stimuli. To achieve transdermal drugdelivery, it is essential to allow drug penetration through this epidermal barrier without disrupting it.
Microneedles (MNs) have garnered attention as a novel transdermal drug delivery system to facilitate efficient
drug absorption through the epidermis. Conventional approaches have utilized metal or silicon-based MNs fortransdermal administration, involving drug coating on the MN surface or drug encapsulation within the MN
structure for release in the skin. However, these methods present drawbacks like the risk of needle breakage
upon application, potentially leaving residual fragments in the skin, which compromises safety.
Recently, interest has shifted towards self-dissolving MNs crafted from materials with high biocompatibility
and safety, where the needles dissolve upon application without leaving residues. This mechanism relies on the
dissolution of needles within the skin's moisture, facilitating drug release. While self-dissolving MNs holdpromise as a novel drug delivery approach, they have yet to be fully realized as pharmaceutical products,
necessitating further research. Specifically, there is a need to establish effective evaluation methods, especiallyconcerning drug permeability assessment, which could enhance our understanding of the efficacy of selfdissolving MNs. For instance, Katsumi et al. [1] has investigated self-dissolving MNs utilizing a low-molecularweight drug alendronate (ALN), which is used for treating osteoporosis. Their assessment includes in vitro ALN
release from MNs, time-dependent dissolution observation via microscopy, microscopy-based characterizationof rat skin penetration, and ALN plasma concentration measurements. However, such approaches lack theability to measure real-time drug penetration through the skin.
Here, we propose a new approach utilizing coherent Raman scattering microscopy [2] to evaluate the skinpermeability of low-molecular-weight drugs delivered by MNs. Coherent Raman scattering microscopy allows
real-time permeability assessment of low-molecular-weight drugs without requiring labeling, which can be
employed to measure the depth and time of drug penetration within skin tissue [3]. In this study, we will focus
on the spatiotemporal kinetics of common low-molecular-weight drugs, such as migraine medications andanesthetics, released from the applied MNs. This non-labeled and real-time drug measurement will contributesignificantly towards evaluating the effectiveness of medical MNs and advancing their practical use.

References:[1] H. Katsumi, Y. Tanaka, K. Hitomi, S. Liu, Y.-S Quan, F. Kamiyama, T. Sakane and A. Yamamoto, “Efficient
Transdermal Delivery of Alendronate, a Nitrogen-Containing Bisphosphonate, Using Tip-Loaded Self-Dissolving
Microneedle Arrays for the Treatment of Osteoporosis,” Pharmaceutics 9, 29 (2017).
[2] J. X. Cheng and X. S. Xie, Coherent Raman Scattering Microscopy (CRC Press, 2013).
[3] T. Ito, R. Iguchi, F. Matsuoka, Y. Nishi, T. Ogihara, and K. Misawa, “Label-Free Skin Penetration Analysis Using TimeResolved, Phase-Modulated Stimulated Raman Scattering Microscopy,” Biomed. Opt. Express 12, 6545-6557 (2021).

NYCU-TUAT-UY Symposium 2023

POS. 06

Electrolysis measurements and evaluation of boron-doped
diamond-coated electrode materials for fuel cells
Yu Okano A, Ken Okano B and Kazuhiko Misawa A
A

Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo, JapanB
Department of Material Science, International Christian University, 3-10-2 Osawa, Mitaka-shi, Tokyo 181-8585, Japan
Author e-mail address: s197660t@st.go.tuat.ac.jp

Abstract: In this study, an alternative electrode material for fuel cells was prepared by coating
conductive boron-doped diamond (BDD) on the surface of a graphite substrate. The
performance was confirmed by electrolysis and evaluated by Raman measurements and SEM
observations before and after electrolysis. The graphite electrode surface was etched after
prolonged electrolysis, while negligible change was observed in the BDD-coated sample. Thissuggests that the BDD coating is useful as an electrode for fuel cells.
1. Introduction
Batteries, especially fuel cells, are essential for the effective use of renewable energy to solve global energy
problems. Various technologies are being developed for the practical application of fuel cells, among which thedevelopment of electrodes with high reaction efficiency and corrosion resistance is very important. Platinum andplatinum group electrodes are attracting attention because of their high exchange current density, but these arerare metals and will not lead to the sustainable spread of fuel cells. Therefore, electrodes made from carbon, which
are abundant on earth, are attracting attention as an alternative to platinum-based electrodes. Carbon has a varietyof allotropes, including the highly conductive but chemically unstable graphite and the generally less conductive
but chemically stable diamond. Previous reports have shown that boron doping of diamond (BDD) lowers its
intrinsic resistance to around 10-3 [Ω-cm] [1]. However, bulk BDD alone cannot be used as an electrode due to its
relatively high resistance. In this study, we attempted to develop an electrode that utilizes the electricalconductivity of graphite and the surface stability of diamond by coating a BDD film on the surface of graphite byvapor-phase growth.
2. Methods
The samples prepared are pure graphite rods (resistance 2 [Ω]) coated with BDD doped with boron trioxide (B2O3),
where the boron doping to carbon in the BDD is 99:1 (R=1900 [Ω]). The reference sample is a pure graphite rod.
The electrical properties of the samples were measured by cyclic voltammetry (CV) [2,3]. In this measurement,
the redox reaction at the electrode surface can be assessed from the voltage-current characteristic. To determine
the durability of the samples in the redox reaction, long-term electrolytic measurements were carried out at a
sweep rate of 4 V/s for 185 hours. Crystallinity and surface uniformity of the graphite were measured nondestructively using a Raman microscope as part of the evaluation of the sample electrodes before and after CV,
and the surface condition was also confirmed using a scanning electron microscope.
3. Results and Discussion
For the graphite sample, the electrolysis results are shown on the left side of Fig. 1 where the current level
decreases after 185 hours (Purple line). SEM observation of the surface before and after electrolysis (Fig. 2 upper
panel) showed the surface roughness after electrolysis. Raman spectral results before and after CV are shown in
Fig. 3. From these Raman spectra, the crystallinity of the graphite sample can be characterized by the D-band(1360 cm-1)/G-band (1580 cm-1) intensity ratio. The D-band/G-band ratio before CV was 0.334 (blue line) and theratio after the CV measurement was 0.165 (light blue line) where a lower D-band/G-band ratio corresponds to abetter crystallinity. This relsult indicates that the electrolysis over a long period of time etched away the lesscrystalline parts of the graphite surface, leaving only the more crystalline parts.
The results of the electrolytic measurements of the BDD samples (right-hand side of Fig. 1) showed nosignificant degradation in the redox reaction after 185 hours. Surface observations by SEM before andafter electrolysis showed no exfoliation (lower part of Fig. 2). The Raman spectra shows a characteristic
peak of diamond at 1332 cm-1. Negligible change was found in the Raman spectra between before (red line
in Fig. 3) and after (pink line) electrolysis. From the higher durability of BDD-coated samples, we concluded
that diamond coating is useful as an electrode in fuel cells.
-6600x10-6

CV for 185h

BBD(99:1)_after4h
BBD(99:1)_after16h
BBD(99:1)_after30h
BBD(99:1)_after57h
BBD(99:1)_after137h
BBD(99:1)_after187h

2.0

200

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Borondoped(99:1)
4mmGraphite

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Current[A]Current[A]400Graphite_after4hGraphite_after16h
Graphite_after40h
Graphite_after65h
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Graphite_after135hGraphite_after185h

Intensity [a.u.]

600x10

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0.4

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Fig. 1: CV experiment results

References

0.0
0.2
Voltage[V]

0.4

0.6

0.8

Fig. 2: Results of surface observations by SEM

500

1000

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-1
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2000

2500

Fig. 3: Raman measurements results[1] K. Okano et al., "Synthesis of diamond thin films having semiconductive properties" Jpn. J. Appl. Phys. 27, pp. L173-175(1988)[2] “Denki Kagaku Sokutei Manyuaru Kiso.” (in Japanese) The Electrochemical Society of Japan, ed., (2002)[3] Noémie Elgrishi et al., “A Practical Beginner’s Guide to Cyclic Voltammetry” J. Chem. Educ.95, 197−206, (2018)

NYCU-TUAT-UY Symposium 2023

POS. 07

Non-Thermal Protein Structural Change
by THz Pulsed Light Irradiation
Kyosuke Makino and Kazuhiko Misawa
Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo, 184-8588, Japan
s229771s@st.go.tuat.ac.jp

Abstract: Terahertz (THz) light that resonates with the vibrational frequency of hydrated
water molecules, can alter functional expression of proteins. Previous studies have shown thathigh-intensity THz light promotes actin fiber formation, but such mechanism is notcomprehensively investigated. Here, we aim to clarify this mechanism by irradiating actin
solution with THz pulsed light of lower average power and higher electric field intensity tosuppress thermal effects. We compare the degree of fiber formation with and without
irradiation.
1. Introduction: Water molecules around proteins form a hydration structure that contributes to the stabilizationof protein structure and functional expression. In general, terahertz (THz) light that resonates with thevibrational frequency of hydrated water molecules, can alter the functional expression of proteins [1,2]. Previous
studies have shown that high-intensity THz light (pulse duration 10 ms, frequency 0.5 THz, maximum
amplitude 1.8 V, average power 0.6 mW/cm2) promotes actin fiber formation [3]. They expected that such fiber
formation resulted from the reconstruction of water hydration network due to the nonthermal effect of THz
excitation for vibrational mode of hydration water. However, this study does not comprehensively clarify
whether the promotion of actin fiber is due to the nonthermal effect of intense electric fields or thermal effects
originating from the temperature rise by THz light irradiation. In this study, we aim to clarify the existence of
non-thermal effects in protein structural change by irradiation with THz pulsed light of lower average power andhigher electric field intensity.
2. Methods: The experimental system is shown in Figure 1. We used a THz light pulse with a pulse width of 34 ps, a center frequency of 0.7 THz, a peak electric field intensity of approximately 80 V and average power
1.8×10-3 mW/cm2 generated by the optical rectification effect of a femtosecond laser (center wavelength: 800nm) using a nonlinear optical crystal (4-N,N-dimethylamino-4-N-methyl-stilbazolium 2,4,6trimethylbenzenesulfonate: DSTMS). Actin fiber formation is initiated by adding buffer containing divalentcations (Ca2+, Mg2+) to monomeric actin solutions. The actin is labeled with pyrene, which increases
fluorescence (excitation at 365 nm, emission peak at 400 nm) as the fiber formation progresses. Then, we
measured fluorescence intensity in 400-500 nm using an optical fiber and a photomultiplier tube (PMT).
3. Results and Discussion: Comparative results (Figure 2) show that the fluorescence intensity was higher for
actin irradiated with THz light, which indicates that the THz light pulses inhibit actin fiber re-decomposition,
probably due to non-thermal effects. The dependence on the resonant frequency of terahertz light is the key tovalidate the non-thermal effect. We will change the irradiation condition of THz frequency to clarify theresonant frequency effect.

Figure 1: Overview of the experimental system

Figure 2: Actin fiber formation with and without THz
light irradiation

References[1] J. Sugiyama, Y. Tokunaga, M. Hishida, et al., Nonthermal acceleration of protein hydration by sub-terahertz irradiation, Nat. Commun.
14, 2825 (2023).
[2] I. V. Lundholm, H. Rodilla, W. Y. Wahlgren, et al., Terahertz radiation induces non-thermal structural changes associated with Fröhlichcondensation in a protein crystal, Struct. Dyn. 1, (2015).
[3] S.Yamazaki et al., Actin polymerization is activated by terahertz irradiation, Sci. Rep. 8, 9990 (2018).

NYCU-TUAT-UY Symposium 2023

POS. 08

Evaluation of the ability of various peptoids
to inhibit amyloid beta aggregation
Ogiriyama Kei and Kazuhiko Misawa
Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei-shi, Tokyo 184-8588
e-mail address: s233864q@st.go.tuat.ac.jp

Abstract: Peptides that inhibit the aggregation of amyloid-β (Aβ), the causative agent of
Alzheimer's disease (AD), have attracted much attention as a treatment for AD. However,
peptides have challenges in protease degradation and cell membrane permeability.
Peptidomimetics are attracting attention to overcome these challenges. In this study, peptides
with Aβ aggregation inhibitory ability are converted to peptoids, one of the peptidomimetics,
and their aggregation inhibitory ability and changes in cell membrane permeability areevaluated. A preliminary experiment showed that Aβ aggregation without peptoids reaches asteady state in 7 hours.
1. Introduction
Peptides have attracted attention as biopharmaceuticals due to their high biocompatibility, specificity, and low
toxicity. Peptide drugs have the potential to be a causative therapy because they can act directly on
neurodegenerative diseases caused by abnormal aggregation of proteins and peptides. Alzheimer's disease (AD)is one of the most common neurodegenerative diseases, and although it is the most common form of dementia,
there is no fundamental cure for it. For this reason, many studies have been conducted to develop therapeutic
agents for AD, including peptides to inhibit the aggregation of the causative agent of Alzheimer's disease(amyloid-β (Aβ)). However, peptides are subject to protease degradation and have low permeability through cell
membranes. Thus, it is important to overcome these disadvantages to use peptides as therapeutic agents.
Peptidomimetics have attracted attention as molecules that overcome these disadvantages while retaining thebiological activity and function of peptides [1]. Peptoids are molecules with side chains shifted from α-carbons tonitrogen. This structure makes them resistant to protease degradation and increases their cell membrane
permeability, which can improve their biocompatibility. A previous study has shown that peptoids preparedfrom peptides with Aβ aggregation inhibition ability could improve the aggregation inhibition ability and bloodbrain barrier permeability [2]. However, it is difficult to conclude that the conversion to peptoids really changed
the characteristics, as the previous study compared only one case.
The purpose of this study is to evaluate the usefulness of peptoids as a therapeutic agent for AD byconverting some peptides that have already been shown to inhibit Aβ aggregation into peptoids. We measure
how their aggregation inhibition ability and blood-brain barrier permeability are altered. The thioflavin T (ThT)
assay is used to evaluate the aggregation inhibition ability. It is known that Aβs form the β-sheet structure whenaggregated, and ThT can specifically produce fluorescence to the β-sheet structure. This allows us to compare
the changes in Aβ aggregation with and without peptoids. Here we present a preliminary experiment without
peptoids and with Aβ only. The result showed that the fluorescence value of ThT increased with aggregation
and reached a steady state after 7 hours.
2. Result and Discussion
250000200000intensity

Aβ was adjusted to 100 μM with DMSO and pure water andincubated at 37°C, shaken at 400 rpm. Fluorescencemeasurements were then performed using ThT every 30
minutes (up to 8 hours) and 24 hours later. The time variationof the total fluorescence values is shown in Figure 1. The
fluorescence value increased with time, indicating that Aβ
aggregation was taking place. The fluorescence value reachedthe maximum after 7 hours and remained almost unchanged
thereafter, indicating that all Aβ in the solution had been fully
aggregated. In the next step, we will measure the aggregationof Aβ when peptoids are added.

150000100000
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10

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time(h)Figure 1 Time variation of ThT fluorescence intensity
during Aβ aggregation

3. References[1] Khalily M.P., Soydan M., WILEY Chem Biol Drug Des.Volume 101, Issue 3,772-793 (2022).
[2] K. Pradhan et al, ACS Chem.Neurosci. 10,1355-1368 (2019).

NYCU-TUAT-UY Symposium 2023

POS. 09

Differential Effects of Continuous and Pulsed UV-C Lighton Bacterial Inactivation in Platelet Concentrates
Shuri Kozuka, Shundai Yamamoto, and Terumasa Ito
Department of Biomedical Systems Engineering, Faculty of Engineering, Tokyo University of Agriculture and Technologys202106z@st.go.tuat.ac.jp

Abstract: Platelet concentrates (PCs) are prone to bacterial growth due to storage at room
temperature. Therefore, an efficient bacterial inactivation technique is desirable. A previous
study has shown that pulsed UV-C light inactivates bacteria more effectively than continuous
UV-C light under the same irradiation dose. However, the cause of the improved inactivation
efficiency has not been elucidated. We show comparative experiments with different UV
irradiation conditions to clarify the mechanism of the improved inactivation efficiency.
Blood products are used in transfusion medicine and must be supplied safely to patients. Among blood products,
platelet products are particularly difficult to control safety. Platelet concentrates (PCs) are stored at room
temperature to maintain hemostatic capacity but are prone to bacterial growth. Transfusion of platelet products
contaminated with bacteria can induce sepsis. Therefore, bacterial inactivation is desirable during the production
and storage of PCs.
One method for inactivating bacteria in PCs is to combine the addition of photosensitizers with UV-A or
UV-B light irradiation, which can achieve a high inactivation effect [1,2]. However, toxic photosensitizers must
be removed after irradiation. There is also a concern that the safety of the chemicals cannot be guaranteed.
Another alternative method that does not require the addition of chemicals is UV-C light irradiation [3]. Thismethod provides an inactivation effect but does not maintain platelet function such as aggregation capacity. To
solve this problem, methods to enhance the inactivation effect by pulsed UV-C irradiation have been proposed[4,5]. Our previous study has shown that pulsed light inactivates bacteria more effectively than continuous lightunder the same irradiation dose of UV-C [5]. However, the mechanism of the improved inactivation efficiency
has not been elucidated.
The aim of this research is to clarify the cause of the higher bacterial inactivation effect of UV-C pulsed lightto find effective inactivation conditions, and to develop efficient inactivation techniques. The difference
between continuous light irradiation and pulsed light irradiation lies in their instantaneous peak power and pulse
energy per irradiation. Which of these enhanced the inactivation effect was not known in the previous study. To
clarify this, two experiments will be conducted. In the first experiment, we will compare the bacterial
inactivation under irradiation conditions in which only the pulse width is changed under the same repetition
frequency of 10 kHz, which will show whether the high peak power of the pulsed light contributes theinactivation enhancement. In the second experiment, we will compare the bacterial inactivation under irradiation
conditions with the same pulse width but with different repetition frequency of the light source. The result willshow the pulse energy dependence of the inactivation efficiency.
Currently, we are revisiting our previous experiment on comparing the bacterial inactivation effects with acontinuous wave LED and a femtosecond pulsed laser. We have confirmed that the effectiveness of the pulsed
UV-C inactivation is reproducible. This presentation will describe two methods to test which parameters ofpulsed light irradiation enhance the inactivation effect.
References[1] J. Irscha and L. Linb, "Pathogen Inactivation of Platelet and Plasma Blood Components for Transfusion Using the INTERCEPT Blood
System™,” Transfus Med. Hemother. 38, 19–31 (2011).
[2] P. H. Ruane, et al., “Photochemical inactivation of selected viruses and bacteria in platelet concentrates using riboflavin and light,”
Transfusion 44, 1537-2995 (2004).
[3] A. Seltsam and T. H. Müller, “UVC Irradiation for Pathogen Reduction of Platelet Concentrates and Plasma,” Transfus. Med. Hemother.
38, 43–54 (2011).
[4] H. Abe, et al. “Pulsed xenon flash treatment inactivates bacteria in apheresis platelet concentrates while preserving in vitro quality andfunctionality,” Transfusion 57, 989-996 (2017).
[5] M. Saiga, et al., “Bacterial Inactivation in Platelet Concentrates Using Ultrashort Pulsed Laser,” Proc. SPIE, 119210J (2021).

NYCU-TUAT-UY Symposium 2023

POS. 10

Real-Time Monitoring of Aspirin Metabolism
Using Raman Microscopy
Ryo Fujisawa and Terumasa Ito
Department of Biomedical engineering Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo, Japans207975s@st.go.tuat.ac.jp

Abstract: Monitoring of aspirin and its metabolite concentrations would be desirable to prevent
poisoning effect while adjusting the dose at the optimum concentration. In this study, we showthat Raman spectroscopy can be used to perform real-time monitoring of aspirin metabolism. A
preliminary spectral measurement of aspirin and its metabolites using confocal Raman
microscopy show that each chemical has different peaks in the Raman spectrum.
1. Introduction
In living organisms, drugs are processed through the processes of absorption, distribution, metabolism andexcretion, which are considered essential for the pharmacological activity and efficacy of administeredchemicals. Among them, metabolism is particularly important because many drugs show efficacy or toxicity
depending on their metabolism. As an example, aspirin, which is an antipyretic, analgesic, and antiinflammatory drug, is mainly metabolized in the liver to salicylic acid. However, excessive aspirin intake canlead to salicylic acid poisoning, which can lead to liver and kidney damage. In fact, in the treatment ofrheumatic fever, the concentration of salicylic acid in the plasma is close to the intoxication range [1]. To
prevent salicylic acid poisoning while adjusting the aspirin dose at the optimum concentration, simultaneous
monitoring of aspirin and salicylic acid concentrations would be desirable.
One conventional analytical method to simultaneously detect aspirin and salicylic acid is liquid
chromatography-mass spectrometry (LC/MS) [2]. However, LC/MS requires complex and laborious sample
processing from sample collection to measurement. Another promising candidate is Raman spectroscopy, which
is a label-free laser spectroscopy to analyze the molecular structure of chemicals by examining frequency-shiftdependence of the scattered light (Raman spectrum). Raman spectroscopy does not require complex processingof the sample and allowing rapid detection of drugs in the body. Therefore, it can be used to determine real-time
aspirin and salicylic acid concentrations for optimizing individual patient dosing.
The aim of this study is to monitor aspirin metabolism in real-time using Raman microscopy. As apreliminary experiment, Raman spectra of aspirin, and its metabolites (salicylic acid and acetic acid) were
measured using confocal Raman microscopy. The results show that the Raman spectra of aspirin, salicylic acidand acetic acid have different peaks.
2. Methods and results
Aqueous solutions of aspirin, salicylic acid, and acetic acid were prepared (aspirin 6.5 mM, salicylic acidsaturation concentration (< 68 mM), acetic acid 1.5mM) and Raman spectra were measured by confocal Raman
microscopy. The results are shown in Figure 1.

(A)
(B)
(C)
Fig. 1. Measured Raman spectra: (A) aspirin, (B) salicylic acid, and (C) acetic acid
3. Discussion
We found that each chemical exhibits a unique, distinct peak: aspirin at 1607 cm-1, salicylic acid at 564 cm-1,
and acetic acid at 890 cm-1. Since these peaks are not found in other substances, monitoring the changes in theintensity of these peaks will allow us to observe aspirin metabolism. As a next step, we will conduct anexperiment to monitor the aspirin and the metabolites while aspirin is hydrolyzed with esterase.
References[1] Bayer Yakuhin K.K., Drug Interview Form “Bayaspirin tablets 100 mg” (2019) (in Japanese)
https://pharma-navi.bayer.jp/sites/g/files/vrxlpx9646/files/2022-05/BAS_IVF_202205120.pdf[2] D. Sirok et al., “Robust and sensitive LC/MS-MS method for simultaneous detection of acetylsalicylic acid and salicylic acid in humanplasma,” Microchemical Journal 136, 200-208 (2018)

NYCU-TUAT-UY Symposium 2023

POS. 11

Analysis of Cellular Transport of Odor Molecules Using
Coherent Raman Scattering Microscopy
Noa Saito and Terumasa Ito
Department of Biomedical Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo, Japans209904u@st.go.tuat.ac.jp

Abstract: Despite the advances in the understanding of olfactory receptors, the detailedtransport dynamics of odor molecules themselves has not been fully understood. Using coherent
Raman microscopy, a high-speed label-free chemical imaging method, we investigate whether
the odorants that bind to receptors are taken up into the cells.
1. Introduction
Advances in olfactory research would help develop odor sensors that enable early diagnosis and preventionof diseases. When an odor molecule enters the nasal cavity, it binds to olfactory receptors and electrical signals
are sent out to recognize the odor. Various odors can be identified by the combined binding of receptors
consisting of about 400 different receptor types. The research focus in this field has been to explore theinteractions between olfactory receptors and odor molecules, where luciferase chemiluminescence reporters areoften used to examine the odor-receptor binding strength. Despite the advances in the understanding of olfactory
receptors, the detailed transport dynamics of odor molecules themselves has not been fully understood. There
are two possible membrane transport pathways: namely, passive diffusion and receptor-mediated transport.
Passive diffusion is considered as the major pathway of odor molecules due to their small size (molecularweight of approximately 200) and lipophilicity. In addition to this, receptor-mediated transport can beconsidered as the second transport mechanism. However, there is no evident report that the olfactory receptor
actively pumps odorants into the cell. The challenge in such research lies in the difficulty in the direct
observation of odor molecules. Due to the small size of odorants, one cannot use labelling such as fluorescencetags since it may alter the transport kinetics and physiological functions, which makes it difficult to monitor the
local concentration of the odor molecules in live cells.
In this study, we analyze the cellular transport of odor molecules using Raman microscopy. Raman
microscopy is a label-free chemical imaging method that can be used for observing small molecules [1].
Conventional Raman microscopy suffers from low sensitivity and does not support real-time small-molecule
detection. However, this issue can be overcome by using coherent Raman scattering microscopy [2], which canamplify the signal intensity via pulsed excitation by up to several orders of magnitude. With this technique, wewill clarify whether the odorants that bind to receptors are taken up into the cells.
2. Methods
To investigate the receptor-mediated transport, cells expressing an olfactory receptor that binds to the target
odorant molecule, and cells expressing another different olfactory receptor with no binding to the odorant are
prepared. We use our developed coherent Raman microscope that is designed to detect small molecules withenhanced signal contrast [2]. If the receptor pumps the odorant into the cells, we should be able to observe an
increased concentration inside the cell, in addition to the passively transported odorants. The measurable
intracellular concentration of the odorant by coherent Raman microscopy is determined by the signal-tobackground ratio, i.e., the ratio of the spectral intensity of the odor molecules to the background spectral
intensity of the cell. Therefore, we first measured the background Raman spectrum of the cell.
3. Results and Discussion
Figure 1 shows the background spectrum of the cultured cells
measured with the coherent Raman microscope. The
spectrum shows a peak around 1000 cm-1 (phenylalanine inproteins) with a relatively large signal. To optimize themeasurement accuracy, an odorant that has a clear peak otherthan this wavenumber area should be selected. Based on thisdata, we will conduct a screening spectral measurement toselect the best model odorant.
[1] Y. Fukutani et al., “Vapor detection and discrimination with a panel ofodorant receptors,” Nature Communications 9, 4556 (2018).
[2] T. Ito et al., “Spectral focusing with asymmetric pulses for high-contrast
pump-probe stimulated Raman scattering microscopy” APL Photonics 3,092405 (2018).

Fig. 1. Raman spectrum of the cells measured by
the coherent Raman microscope.

NYCU-TUAT-UY Symposium 2023

POS. 12

Improvement of kinetic energy conversion via laser
induced bubble by pulse shaping
Yuki Uchiyama1, Satoshi Honma1, Hironori Ito1
1

University of Yamanashi, 4-4-37, Takeda, Kofu, Yamanashi, 400-8510, Japan
E-mail: hito@yamanashi.ac.jp

Abstract: When a laser beam is focused on a liquid, bubbles are known to be generated andliquid motion occurs. This technology is expected to be applied to medical analysis
technology and cooling technology for electronic components. The problem with thistechnology is the optical-kinetic energy conversion efficiency. In this study, we demonstrate
the superiority of multiphoton excitation by comparing the growth rate of bubbles generated
by a femtosecond pulsed laser and a continuous wave laser of the same energy.
1. Introduction
When a laser beam is focused on a small area in a liquid, an extremely high thermal gradient is generated, which
induces liquid motion such as expansion and contraction motion [1], and Marangoni convection [2]. This
technology is expected to be applied to medical analysis technology, liquid jet scalpels for surgery, and coolingtechnology for electronic components. Energy not converted to kinetic energy becomes heat, damaging thesample and reducing energy conversion efficiency. Therefore, it is necessary to increase the efficiency of
optical-kinetic energy conversion. In this study, we focused on multiphoton excitation induced by femtosecond
pulse lasers (fs laser). The rapid thermal gradient due to multiphoton excitation is expected to significantly
improve the kinetic energy conversion efficiency. The growth rates of bubbles generated by fs laser andcontinuous-wave (CW) laser at the same energy were compared to demonstrate the improvement in opticalkinetic energy conversion efficiency by multiphoton excitation.
2. Experimental Methods
The optical system shown in Fig. 1 is designed and constructed to generate bubbles in a liquid by a laser and toobserve them. A CW laser with a wavelength of 800 nm and a fs laser with a repetition rate of 76 MHz, a center
wavelength of 800 nm, and a pulse width of 15 fs were used as the light sources for bubble generation. Theselasers were focused onto a dye precipitate in acetone solution containing methyl elongate using an objective lensto generate bubbles. A bandpass filter transmitting light between 400 nm and 600 nm was used to prevent
scattering of the laser beam. A CMOS camera was used for observation.
3. ResultFig. 2 shows the bubble generation during (a) continuous CW laser irradiation and (b) continuous fs laser
irradiation at 200 mW. In the case of fs laser irradiation, emission from two-photon excitation that passed
through the filter can be confirmed near the focal point. Fig 3 shows the laser power dependence of the bubble
growth rate under CW and fs laser irradiation. At 220 mW and 240 mW, the growth rate of bubbles increases
rapidly when irradiated by the fs laser. This indicates that the fs laser irradiation generates bubbles with highefficiency via two-photon excitation.

Fig. 1 Optical setup for laser focusing andobservation

Fig. 2 CMOS images of bubble generationby (a) CW laser, (b) fs laser

Fig. 3 Laser power dependence of
bubble growth rates

4. Conclusion
In this study, the efficiency of bubble generation in single-photon excitation and two-photon excitation wascompared by comparing the bubble generation rates in CW and fs lasers. As a result, it was found that bubbles
were generated more efficiently with two-photon excitation.
5. References[1] Y. Mizushima et.al., Appl. Phys. Lett. 107 114102 (2015).
[2] K. Namura et.al., Scientific Reports 9 4770 (2019).

NYCU-TUAT-UY Symposium 2023

POS. 13

Control of lattice vibrations by carrier-envelope phasemodulation of terahertz pulses
Ryuta Watanabe1, Satoshi Honma1 and Hironori Ito1
1

University of Yamanashi, 4-4-37, Takeda, Kofu, Yamanashi, 400-8510, Japan
E-mail: hito@yamanashi.ac.jp

Abstract: This presentation suggests a fast control of lattice vibrations by modulating the carrier
envelope phase of double terahertz pulses using a modified Michelson interferometer. A
resonant EO sampling technique is also proposed to dynamically observe the instantaneous
stopping of oscillating lattice vibrations.
1. Introduction
Currently, methods to excite lattice vibrations by electromagnetic pulses at terahertz frequencies (THz pulse) are
attracting attention. Recently, it has been reported that lattice vibrations can induce physical properties such as
superconductivity [1] and magnetic fields, and there is a possibility that these properties can be controlled at highspeed by controlling lattice vibrations with THz pulses.
In previous study, a single THz pulse is used to induce lattice vibrations [2] as shown in Fig. 1(a). In this study, asecond THz pulse is introduced as shown in Fig. 1(b). Furthermore, by manipulating the carrier envelope phaseof the second THz pulse, we propose a method to instantly stop the lattice vibration and control it at high speed.
The realization of this method is expected to speed up the control of physical properties associated with lattice
vibrations. In this study, the generation of double terahertz pulses will be aimed for, lattice vibration will be
induced, oscillation will be controlled and halted, and the oscillation will be observed.

(a)

(b)

Fig. 1 Schematic diagram of controlling lattice vibration with THz pulse. (a) For single pulse, a lattice vibrationis generated. (b) Lattice vibration stops instantly at the second THz pulse with adjusted carrier- envelope phase.
2. Resonant EO sampling for observation of lattice vibration
An observation method is proposed for lattice vibrations controlled at high speed by two terahertz pulses, by EO
sampling resonant to the vibrational mode.EO sampling is usually used to measure the instantaneous electric fieldof THz pulse.Incident of the THz pulse to be observed into an electro-optical crystal distorts the lattice and causes
birefringence due to the piezoelectric effect.This anisotropy of the refractive index can be detected as a change inthe polarization of the simultaneously injected probe light fs pulse to measure the instantaneous electric field of
THz pulse.
The temporal variation of the THz pulse is obtained by shifting the delay time of the probe light.In the case of
intrinsic vibrations of the electro-optical crystal within the bandwidth of the incident THz pulse, the lattice
vibrations themselves can be observed, although the electric field intensity will not be measured correctly.The
suggestion is to use quartz crystals as electro-optic crystals for EO sampling.The terahertz pulses used in thisexperiment have a centre frequency of about 0.1-10 THz, which resonates with the vibrational mode of the 3.1
THz infrared activity of quartz.
The peak of the vibrational mode is sharp and has a lifetime of about 10 ps.The electro-optical coefficient ofquartz is small and not suitable for intrinsic EO sampling, but is increased by the intrinsic vibration and can bedetected.The first terahertz pulse will be used to induce vibrational mode in the quartz crystal, and the carrier
envelope phase of the second pulse will be adjusted to stop the vibrational mode.
3. References[1] T. F. Nova, A. Cartella, A. Cantaluppi, M. Forst, D. Bossini, R. V. Mikhaylovskiy, A. V. Kimel, R. Merlin, and A. Cavalleri, “An effective
magnetic field from optically driven phonons,” Nat. Phys. 13, 132–136 (2017)[2] C. Vicario, A. Trisorio ,S.Allenspach, C.Ruegg,and F.Giorgianni1 "Narrow-band and tunable intense terahertz pulses for mode-selective
coherent phonon excitation" Appl. Phys. Lett. 117, 101101(2020)

NYCU-TUAT-UY Symposium 2023

POS. 14

SQAM signal retrieval for holographic memory
using a spatial partial filter based on IFTA
Akihiro Yamashita1, Hironori Ito1, Satoshi Honma1
1

University of Yamanashi, 4-4-37, Takeda, Kofu, Yamanashi, 400-8510, Japan
E-mail: shonma@yamanashi.ac.jp

Abstract: We propose a retrieval method based on IFTA to detect SQAM signals with simple
optics, by blocking a part of the reconstructed beam with a spatial partial filter. The numericalanalysis shows our technique can retrieve SQAM data with less embedded data.
1. Introduction
The recording scheme of spatial quadrature amplitude modulation (SQAM) signals improve the density ofholographic data storages (HDS) [1]. One method based on Iterative Fourier Transform Algorithm (IFTA), which
retrieves the phase from the intensity distribution in the Fourier plane of the reconstructed beam without opticalinterferometers was proposed [2]. However, to achieve sufficient accuracy, a certain amount of known data
(embedded data) must be embedded in the recorded data. This reduces the effective storage capacity.
In this paper, we propose a novel IFTA method to reduce the amount of embedded data by blocking a part of thereconstructed beam with a spatial partial filter. It reduces storage loss due to embedded data.
2. IFTA method using a spatial partial filter
The reading process is shown in Fig. 1. The SQAM signal is reconstructed from the HDS. After passing throughthe lens, the beam enters the spatial partial filter in the object domain. The light near the boundary of each data
area is blocked by the filter. On the other hand, the light in the embedded data area is transmitted without being
blocked. After the beam passes through the lens again, the Fourier intensity 𝐼𝐹 is captured by a CMOS sensor.
The retrieval process of complex amplitude based on IFTA is described in Fig. 2. 𝑔𝑘 indicates an estimate SQAM
signal data. Then, the value of 𝑔𝑘 is replaced with embedded data. After the substitution, obtained distribution isredefined by 𝑔′𝑘 . Executing the Fourier transform on 𝑔′𝑘 , we obtain 𝐺𝑘 on the Fourier domain. After replacing|𝐴𝐹_𝑘 | with the square root of the Fourier intensity IF, the distribution is redefined by 𝐺′𝑘 . By performing theinverse Fourier transform on 𝐺′𝑘 , we obtain the 𝑔𝑘+1 , which is the new estimate for the iteration.
3. Numerical analysis of SQAM signals retrieval
We evaluated the retrieval accuracy for 10 pages of SQAM signal composed of 64 × 64 symbols, with 4-level
phase and 2-level amplitude values. The area of a symbol was defined as 𝐿 × 𝐿, and the transmission area of thespatial partial filter was (𝐿/2) × (𝐿/2).
The number of iterations until the symbol error rate (SER) reaches 0 % under different embedded rate is plottedin Fig. 3. As the embedded rate decreased, the iterations required for retrieval increased. Our method can retrieve
the data with 10 iterations and 20 % embedded rate. However, the conventional method requires 50 % embedded
rate to retrieve data within 10 iterations.
4. Conclusions
We proposed a retrieval method for the SQAM signal using the spatial partial filter and IFTA. Our method canretrieve SQAM data with less embedded data, comparing with the conventional method.
5. References[1] S. Honma and H. Funakoshi, “Reproduction of SQAM signal for holographic memory and Estimation of recording density”, IEICE
technical report, 2020, vol. 119, no. 421, pp. 283-288.
[2] C. Yu, S. Wang, R. Chen, J. Hao, Q. Zheng, J. Wang, X. Qiu, K. Wang, D. Lin, Y. Yang, H. Li, X. Lin, and X. Tan, “Improved phaseretrieval in holographic data storage based on a designed iterative embedded data”, Front. Optoelectron 14, 2021, pp. 529-539.

Fig. 1 Reading process

Fig.2 Retrieval process of IFTA

Fig.3 Numerical analysis result

NYCU-TUAT-UY Symposium 2023

POS. 15

Decoding method with simultaneous reconstruction of
SQAM signals for holographic data storage
Yunosuke Shimizu, Hironori Ito, Satoshi Honma
University of Yamanashi,4-4-37, Takeda, Kofu, Yamanashi, 400-8510, Japan
E-mail: t20ee025@yamanashi.ac.jp

Abstract: We propose a simple optical system to decode complex amplitude of thereconstructed SQAM signal by simultaneously reproducing multiple SQAM signal beams anddetecting the interference fringe of the beams. We estimate the quality of the detected complex
amplitude of the signal by the numerical analysis.
1. Introduction
Many researchers have investigated recording schemes of spatial quadrature amplitude modulated (SQAM)
signal to increase the capacity of holographic data storage (HDS). Optical interferometers are in general used tomeasure the phase of the reconstructed signal light, which complicates the optical system.
In this report, we propose a new decoding method of the SQAM signals, in which multiple SQAM signal are
simultaneously reproduced from HDS and the interference fringe pattern are detected by camera, without external
optical interferometer. The phase distribution of the signals is measured by analyzing the fringe pattern. In thefollowing, we evaluate the estimation accuracy of the reproduced distributions.
2. Recording process of SQAM signal and decoding process by simultaneous reconstruction
Figure 1 shows a recording process of the SQAM signals. The signal Fourier transformed by a lens and thereference light are irradiated on the holographic disc, and the hologram is recorded. And then, the series ofholograms are recorded by the same process, rotating the disc.
Figure 2 shows a schematic diagram of the simultaneous reconstruction of two SQAM signals and the decoding
the complex amplitude of the signal. The two holograms are simultaneously readout and then the interference
pattern of the reproduced signal beams are detected by the camera. Implementing Fourie fringe analysis to thepattern, we obtain the distribution corresponding to 𝐶2 𝐶1∗ , where 𝐶𝑖 (𝑥, 𝑦) is the complex amplitude value of each
SQAM signal recorded in holographic memory and the subscript 𝑖 = 1,2 are the label number of the holograms[1].
Here, if the distribution of 𝐶1 is known in advance, 𝐶2 can be calculated by dividing 𝐶2 𝐶1∗ by 𝐶1∗ .
3. Evaluation of estimation accuracy
We assume the SQAM signal, composed of 32 x 32 pixels, whose amplitude and phase are modulated to twolevels of 0.5, 1 and four levels of 0, 𝜋/2, 𝜋, 3𝜋/2, respectively. The SQAM signal corresponding to 𝐶1 and 𝐶2
are reproduced from the adjacent holograms, and then the 𝐶2 is decoded by our technique with 𝐶1 . The calculation
result of it is shown in Fig. 3. Although distortion occurs near the boundary of each pixel, it can be confirmedthat the complex amplitude value is estimated with relatively high accuracy.
The estimated signal can be used to decode adjacent neighboring holograms. As a result, all holograms in theholographic memory can be sequentially decoded while the disk is rotated and reproduced.

Fig.1. Recording process

Fig.2. Reading process

Fig.3 Decoded SQAM signals using known 𝐶1

4. Conclusions
We designed the simple optical system to detect the phase distribution of the SQAM signal without an opticalinterferometer. It was shown that if the distribution of one SQAM signal is known, the other SQAM signal
distribution can be decoded with relative
ely good accuracy from the interference pattern between the signals.
5. References[1] M. Takeda, H. Ina, and S. Kobayashi, “Fourier-transform method of fringe-pattern analysis for computer-based topography andinterferometry,” J. Opt. Soc. Am., 72, pp.156-160 (1982).

NYCU-TUAT-UY Symposium 2023

POS. 16

Energy Transfer Between Quantum Dots and Monolayer
MoS2 Studied by Ultrafast optical Pump-Probe Spectroscopy
Yi-Hung Lin1, Yu-Chan Tai1, Jhen-Dong Lin1, Bo-Jun Lai1+, Ruei-Jhe Tu1, Shao-Yu Chen2,3, Chun-Liang
Lin1, Shun-Jen Cheng1, Chih-Wei Luo1
1

Department of Electrophysics, National Yang Ming Chaio Tung University, Hsinchu, 30010, Taiwan
2
Center of Atomic Initiative for New Materials, National Taiwan University, Taipei, 10617, Taiwan
3
Center for Condensed Mater Science, National Taiwan University, Taipei, 10617, Taiwan
Email: zach.sc11@nycu.edu.tw

Abstract: We observed the nonradiative energy transfer (NRET) in the hybrid structure of semiconducting
quantum dots (QDs) spin-coated on a monolayer (ML) molybdenum disulfide (MoS2). This study investigated theultrafast dynamics of excitons in the ML MoS2 with and without the QDs using optical pump-probe spectroscopy(TRS). From photoexciting the heterostructure of QDs/MoS2, we obtained a faster relaxation and a longer lifetimein the transient transmission spectra. By inspecting the energy levels of QDs and ML MoS2, we address the dipoledipole coupling between QDs and ML MoS2 as the observation of NRET that appeared in the photoexcitedheterostructure of QDs/MoS2.

Normalized transient transmission spectra from heterostructure of QDs (CdSe) / MoS2. Inset: heterostructure of
QDs/MoS2

NYCU-TUAT-UY Symposium 2023

POS. 17Ultrafast dynamics of CrMnFeCoNiOx thin film by
pump-probe spectroscopy
Hsing-Yu Yeh1, Chien-Ming Chen1*, Wen-Yen Tzeng2, Wei-En Ke3,
Yu-Chan Tai2, Ying-Hao Chu3, Chih-Wei Luo1,2
1

Department of Physics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
3
Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan* Presenter: Chien-Ming Chen, Email: chienming.sc11@nycu.edu.tw
2

Abstract:
We present a temperature-dependent two-color optical pump-probe spectroscopy study of thehigh-entropy alloy oxide, CrMnFeCoNiOx films. Transient reflectivity changes reveal damped
oscillations spanning 300 K to 20 K, with extracted natural frequencies using fast Fouriertransform. Damped sine function modeling characterizes oscillation lifetimes. Notably, a
speculated phase transition around 160 K is indicated by consistent lifetimes. Our report sheds
light on oscillation generation and data analysis through pump-probe spectroscopy of
CrMnFeCoNiOx films.

Figure . Using pump probe spectroscopy experiment on (a) Epitaxial (b) Amorphous
type thin film in the range of delay time from 0 to 600 ps.

NYCU-TUAT-UY Symposium 2023

POS. 18

Encoding information into Terahertz pulses via spectrally
modulated ultrafast optical pulses
Ching-Wen Wang1, Nai-Hao Chiang2 ,Yu-Chan Tai2, Wei-Hong Huang2, Chih-Wei Luo2
1
Department of Physics, National Yang Ming Chiao Tung University, Hsinchu 300, Taiwan.
Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 300, Taiwan.
c311658011.sc11@nycu.edu.tw; cwluoep@nycu.edu.tw

2

Abstract: We tried to achieve Terahertz communication through photoconductive antenna(PCA) working at 800-nm ultrafast optical pulses. Encoding a set of bit-wise information into
the waveform of single THz-pulse, which was generated by a PCA. The bit-wise information
was encoded via a spatial light modulator (SLM) in frequency domain before thephotoexcitation of the PCA. We utilized a grating to split the optical pulses to frequency
domain, and employed a SLM to modulate the spectral intensity of optics pulses. The spectral
frequency of pulses can be determined to pass or to be blocked by the designed pattern of theSLM. The selectively modulated pulses will stimulate the PCA and generate corresponding
THz waveforms. Our simulation demonstrates that THz waveforms exhibit varying responses
under different spectrally modulated injected pulses.

Figure 1. The schematic of spectrally modulated ultrafast optics pulsed before the photoexcitation of the PCA.

NYCU-TUAT-UY Symposium 2023

POS. 19

Using Mid-Infrared Pulses via Four-Wave Difference
Frequency Generation to Observe Catalytic Materials
Chun-Ying Lin1, Chien-Ming Chao2, Wei-Hong Huang1, Chih-Wei Luo1, Yu-Jung Chen2, Meng-Fan Luo2
1

Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 300093 Taiwan
2
Department of Physics, National Central University, Taoyuan City 320317, Taiwan
Author e-mail address: chunying.sc11@nycu.edu.tw

Abstract: We will focus two-color filamentation to generate mid-infrared (MIR) pulses via four-wave
difference frequency generation [1] and make the MIR pulses as probe beam for measurement. To minimize
dispersion of MIR pulses, we will decrease using transmissive optical components in our system. For thedetection part, we can use a reference beam to have collinear focus with our MIR light source for up-converting
photon energy from MIR region to visible region through gaseous medium [2]. This up-conversional method ismore convenient and quicker to measure MIR spectrum based on the detected up-conversional visible spectrum.
To monitor reactions within MIR region and check mass spectroscopies simultaneously, a near-ambient pressure(NAP) reaction cell was required, and that was installed inside the ultrahigh vacuum (UHV) chamber. The NAP
and UHV chamber were designed by our team member of NCU. This UHV chamber can be used to observe thedynamics of catalytic reactions which occurred on the surface of sample [3]. In our plan, the sample was Rh
nanoparticles which were grown on NiAl substrate with a AlO3 coating. We will expose methanol on the surface
of sample to have decomposition reaction. The overall configuration was shown in Figure 1.

Figure 1. The setup of the MIR pulses generation coupling with UHV chamber system.

References[1] Fuji, Takao, and Toshinori Suzuki. “Generation of sub-two-cycle mid-infrared pulses by four-wave mixing through filamentation inair.” Optics letters 32.22, 3330-3332. (2007)[2] Y. Nomura, Y.-T. Wang, T. Kozai, H. Shirai, A. Yabushita, C.-W. Luo, S. Nakanishi, and T. Fuji, "Single-shot detection of mid-infrared
spectra by chirped-pulse upconversion with four-wave difference frequency generation in gases," Opt. Express 21, 18249-18254 (2013)[3] Yunshu Du, Ling Li, Xuan Wang, and Hengshan Qiu, “A Newly Designed Infrared Reflection Absorption Spectroscopy System for In
Situ Characterization from Ultrahigh Vacuum to Ambient Pressure, ” Appl. Spectrosc. 72, 122-128 (2018)

NYCU-TUAT-UY Symposium 2023

POS. 20

Study of Ultrafast Dynamics in Tb2Te5 single crystal Using
Time-Resolved Spectroscopy
Hsing-Yu Yeh1*, Wen-Yen Tzeng2, Nguyen, Nhat-Quyen2, Yu-Chan Tai2, Chih-Wei Luo1,2
1
Department of Physics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
Presenter: Hsing-Yu Yeh, Email: juststartyo@gmail.com

2

Abstract:
Layered rare earth (R) tellurides layered single crystal RTe n (n=2, 2.5, 3) are considered to be
charge density wave (CDW) materials. To gain a better understanding of the ultrafast
dynamics of Tb2Te5 and determine whether it exhibits CDW behavior, we employed dualcolor pump-probe time-resolved spectroscopy at various tem peratures, as well as lowtemperature X-ray diffraction. In the temperature range of 8 K to 100 K, the transientreflectivity changes (ΔR/R) exhibit a 3.77 THz oscillation mode, and there are distinct trends
in the variations of the b-axis length around the temperature of 120 K in the low-temperature
X-ray diffraction results. By comparing these findings to CDW-like properties observed inother CDW materials, we conclude that Tb2Te5 can be classified as a CDW material, with anestimated CDW phase transition temperature (TCDW) falling in the range of 100-120 K.

200 K
180 K
160 K
140 K
120 K
110 K
100 K
90 K
80 K
70 K
60 K
50 K
40 K
30 K
20 K
15 K
10 K
8K
6K
4K
2K
1.7 K

1.5
1.0
0.5
0.0
-1

0

1

2

3

Delay time (ps)

4

200 K
180 K
160 K
140 K
120 K
110 K
100 K
90 K
80 K
70 K
60 K
50 K
40 K
30 K
20 K
15 K
10 K
8K
6K
4K
2K
1.7 K

Amplitude (arb. units)

DR/R (x10-5)

3.77 (THz)02

4 6 8 10 12 14
Frequency (THz)

Figure. 1. (a) Pump-probe spectroscopy result in Tb2Te5 (b) FFT resultin temperature of 1.7 K to 200 K

NYCU-TUAT-UY Symposium 2023

POS. 21Ultrafast Carrier Dynamics of the Grain Boundaries in
LSMO Homostructure by Spatial Resolved Ultrafast
Pump-Probe Spectroscopy
Jia-Yuan Sun1*, Wen-Yen Tzeng1, Yu-Chan Tai1, Jan-Chi Yang2, Chih-Wei Luo1
1

Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
2
Department of Physics, National Cheng Kung University, Tainan, Taiwan* Presenter : Jia-Yuan Sun, email:scu1027@gmail.com

Abstract: Perovskite manganites are known as functional materials showing colossal
magnetoresistance (CMR) and one of perovskite-LaSr1-xMnxO3 (LSMO) is kind of classic
half-metallic oxide that exhibits large spin polarization and CMR effect. Recent researchshows that an unconventional butterfly-shaped hysteresis magnetoresistance is observed ingrain boundaries of LSMO homostructure, to further exploit its potential, we study thequasiparticle dynamics of the LSMO homostructure with the spatial resolved ultrafast pumpprobe microscopy.

NYCU-TUAT-UY Symposium 2023

POS. 22

Study of the ablation thresholds of monolayer MoS2 fromfemtosecond to picosecond regime
Yin-Huan Gao1, Li-Yang Jiang1, Yu-Chan Tai1, Chih-Wei Luo1,2,3,4,5
1

2

Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 300, Taiwan.
Institute of Physics and Center for Emergent Functional Matter Science, National Yang Ming Chiao Tung University, Hsinchu 300, Taiwan.
3
National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan.
4
Taiwan Consortium of Emergent Crystalline Materials (TCECM), National Science and Technology Council, Taiwan.
5
Department of Physics, University of Washington, Seattle, Washington 98195, USA.
liyangjiamg.sc11@nycu.edu.tw; cwluoep@nycu.edu.tw

Abstract: We utilized a single-shot pulsed laser to ablate monolayer MoS2, employing both
Ti:sapphire and Yb-KWG lasers. Ablation areas were measured under varying dispersion conditions.
The Ti:sapphire laser covered a pulsewidth range from 60 fs to 2 ps, while the Yb-KWG laser, withmultiplate compression (MPC), covered a range from 4.9 fs to 97 fs. Through the relationshipbetween ablation area and pulse energy, we calculated spot sizes and ablation thresholds under
different dispersion conditions. Our observations show a decrease in the ablation threshold as
pulsewidth decreases. This ablation thresholds-pulse dispersion relation was categorized into threeintervals; ionization mechanisms, coulomb interaction in the many-body effect, and bandgap
renormalization effects can explain each trend

References[1] J. M. Liu, “Simple technique for measurements of pulsed Gaussian-beam spot sizes “, Optics. Letters 7(5), 196-198, (1982).

NYCU-TUAT-UY Symposium 2023

POS. 23

Ultrafast Electron Dynamics in 1T-TiSe2 by Tr-ARPES
Shih-Chi Hung1,2, Zhi-Ling Chen1,2, Sheng-Chiao Wang1,2, Hao-Hsiang Jia2,3 , Woei-Wu Pai4
Chih-Wei Luo1, Ping-Hui Lin2
1

Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
2
National Synchrotron Radiation Research Center, Hsinchu, Taiwan
3
Institute of Photonics Technologies, National Tsing Hua University, Hsinchu, Taiwan
4
Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
shih.sc11@nycu.edu.tw

Abstract: Investigating the underlying mechanism of the charge density wave (CDW)phenomenon is crucial in condensed matter physics. We study the ultrafast electron dynamics
in 1T-TiSe2 within femtosecond scale via time- and angle-resolved photoelectron
spectroscopy (Tr-ARPES). By extracting the transient evolution of the electron population, we
provide a dynamic figure to describe the electron-hole pair generation and the electron-phonon
interaction within TiSe2.
1. Introduction
Charge density waves (CDWs) are an important part of the phase diagrams of many related electronicsystems[1]. CDW materials undergo phase transitions at low temperatures, resulting in new electron density
translational periodicity and periodic lattice distortion (PLD). In TMD 1T-TiSe2, the phase transition occurs
below Tc=200 K [2]. Therefore, the understanding of the CDW transition mechanism of this material has
attracted considerable interest, especially for its driving mechanism. Meanwhile, some theoretical models haveexhibited that the stability of CDW can be mutually reinforced through the combined effects of interband
Coulomb interactions and electron-phonon coupling. Investigating the underlying mechanism of the CDW
phenomenon is crucial in condensed matter physics. We performed time- and angle-resolved photoelectron
spectroscopy (Tr-ARPES) measurements to resolve the ultrafast electron dynamics in 1T-TiSe2 in CDW andnormal phase. Through comparing the transient electron population within particular energy and momentum, weare able to track the temporal evolution and scattering pathway of the photoexcited electrons in both CDW andnormal phases.
2. Figures
(a)

(c)

(d)

(e)

(b)

Figure 1. Crystal structure and electronic band structure of TiSe 2 measured by Tr-ARPES (a) Brillouin zones of TiSe2 (b)Representation of two-dimensional at theplane. (c-e) Band dispersions along high symmetry A-L direction, probed with 42 eV attimezero after 800 nm excitation. The spectra were obtained with temperatures and fluences of (c) 78 K and F = 0.70 mJ/cm2, (d) 78 K and F= 0.09 mJ/cm2, (e) 300 K and F = 2.23 mJ/cm2, respectively. The red solid lines obtained from Ref. [3][4] for the calculated band structure
in CDW and non-CDW phases.

3. Equations

4. References[1] H.Hedayat, Excitonic and lattice contributions to the charge density wave in 1T-TiSe2 revealed by a phononbottleneck (Phys. Rev. R,2019), 1,023029.
[2] Monney C, Puppin M. Revealing the role of electrons and phonons in the ultrafast recovery of charge density wave correlations in 1TTiSe2. (Phys. Rev. B.,2016), 94,165165.
[3] T. Jaouen, Phase separation in the vicinity of Fermi surface hot spots (Phys. Rev. B,2019), 100, 075152.
[4] Maria Hellgren, Critical Role of the Exchange Interaction for the Electronic Structure and Charge-Density-Wave Formation in
TiSe2 (Phys. Rev. L,2017), 119, 176401.

NYCU-TUAT-UY Symposium 2023

POS. 24

Terahertz Emission Spectroscopy ofTopological Material EuCd2As2 Single Crystals
Yi-Cheng Cheng1, Po-Wei Gong1, Pei-Tsung Yang1, Xin-Yun Chang1, Jiun-Haw Chu2,
Cheng-Chien Chen3, Jiunn-Yuan Lin4, Chih-Wei Luo1, and Chien-Ming Tu1
1

Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 300093 Taiwan
2
Department of Physics, University of Washington, Seattle, WA, 98195 USA
3
Department of Physics, University of Alabama at Birmingham, Birmingham, AL, 35294 USA
4Institute of Physics, National Yang Ming Chiao Tung University, Hsinchu, 300093 Taiwan
Author e-mail address: (8-point type, centered, italicized)

Abstract: We use the terahertz emission spectroscopy to study the ultrafast carrier dynamics of
EuCd2As2 single crystal, by changing the helicity of incident optical pulses. By time domain
decomposition and recombination, circular photogalvanic effect (CPGE) signal originated fromspin-polarized currents were obtained. The CPGE signal strongly depend on the incident angle
of incident optical pulses, and almost no CPGE signal was observed at normal incident case.
These observations agree with the features of a two-dimensional electron system. Rashba effectwould be a potential candidate for these observations on EuCd2As2 single crystals at room
temperature.

Figure 1. Use quarter wave plate alpha-scan with 45 degree incidence analysis. (A) time-domain terahertz signals under different helicities,(B) extracting positive peaks for model fitting, (C) comparison of fitting parameters, (D) Fourier transform into terahertz spectrum under
different helicities, (E) 2D contour plot of frequency-domain spectrum versus angle, (F) Ratio of absolute values of fitting parameters.

(1)
References[1] N. P. Armitage, et al,” Weyl and Dirac semimetals in three-dimensional solids”, Rev. Mod. Phys. 90. 015001 (2018)[2] Yuto Kinoshita, et al,” Terahertz radiation by subpicosecond spin-polarized photocurrent originating from Dirac electrons in a Rashbatype polar semiconductor”, Phys. Rev. B 97. 161104 (2018)[3] J.-Z. Ma, S. M. Nie , C. J. Yi, et al., “Spin fluctuation induced Weyl semimetal state in the paramagnetic phase of EuCd 2As2,” Scienceadvances, vol. 5, no. 7, eaaw4718 (2019)

NYCU-TUAT-UY Symposium 2023

POS. 25

Generation of circularly polarized THz dual pulses
Yu-Ting Lin1†, Hao-Keng Wei1, Hironori Ito2, Wei-Hong Huang1, Zai-Wen Chen1, Ying-Kuan Ko1,
Chien-Ming Tu1, Atsushi Yabushita1, Kazuhiko Misawa3,4, Chih-Wei Luo1,5,6,7,8
1Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
2Graduate Faculty of Interdisciplinary, Research Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Yamanashi, 400-8511,
Japan.
3Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo, 184-8588, Japan.
4Department of Biomedical Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo, 184-8588,
Japan. 5Taiwan Consortium of Emergent Crystalline Materials (TCECM), National Science and Technology Council, Taiwan.
6Institute of Physics and Center for Emergent Functional Matter Science, National Yang Ming Chiao Tung University, Hsinchu, 30010,
Taiwan.
7National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan.
8Department of Physics, University of Washington, Seattle, Washington 98195, USA.
Author e-mail address† : yuting.sc11@nycu.edu.tw

Abstract: Since high-data-rate communication is desired, to realize terabit (Tbit) wirelesstelecommunication, such as 6G and beyond, new technology is being developed, and it may
well rely on THz photonics. By Shannon’s Capacity Theorem [1], a high frequency channel
has a larger bandwidth and can carry more information than a channel at a lower frequency.
Therefore, the carrier frequency of communication has been raised from megahertz (MHz) to
sub-THz in present telecommunication systems [2]. However, the generation of circularly
polarized (CP) THz waves remain rare, especially for high output power. In this work, wereport a simple and reliable system with Michelson interferometer (MI) for the generation of
circularly polarized (CP) THz dual pulses with variable helicity, frequency, and interval
between pulses [3,4]. These degrees of freedom allow us to arbitrarily control the THz dual
pulses of interests, which has potential applications in imaging, spectroscopy, and in nextgeneration communications.

Fig. 1. Schematic diagram of PTP/PTDP generation and characterization system and to obtain the 3D plots of the THz pulses.

References[1] C. E. Shannon, "A mathematical theory of communication, " The Bell Syst. Tech. J. 27, 379 (1948).
[2] M. Z. Chowdhury et al, "6G wireless communication systems: applications, requirements, technologies, challenges, and research
directions" IEEE Open J. Commun. Soc. 1, 957 (2020).
[3] H. -K. Wei, et al., "Generation and manipulation of polarization-twisting dual pulses with a high degree of freedom, " Opt. Lett. 45, 6663
(2020).
[4] H.-K. Wei, et al., "Few-cycle THz wave manipulation with a high degree of freedom via f-t modulation," Opt. Lett. 48, 1016-1019(2023)

NYCU-TUAT-UY Symposium 2023

POS. 26

Photoinduced evolution of effective mass in 1T-TiSe2
Zhi-Ling Chen1,2, Shih-Chi Hung1,2, Sheng-Chiao Wang1,2, Hao-Hsiang Jia2,3,Woei-Wu Pai4,
Chih-Wei Luo1,*, Ping-Hui Lin2,*
1Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
2National Synchrotron Radiation Research Center, Hsinchu, Taiwan
3Institute of Photonics Technologies, National Tsing Hua University, Hsinchu, Taiwan
4Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
lynn.sc11@nycu.edu.tw

Abstract: We performed the ultrafast electron dynamics of the charge density wave (CDW) material 1TTiSe2 using the time- and angle-resolved photoemission spectroscopy (TR-ARPES) system. The
experimental results provide a direct visualization of the Ti-3d conduction band and the corresponding
evolution of effective mass as a function of pump fluence. The data show that the effective mass of the
Ti-3d electron pocket become heavier as pump fluence increase, which indicates the degree of CDW
phase destroyed at different photoexcitation densities. We also present the time evolution of Ti-3d bandand the change of effective mass suggest the recovery of the CDW phase.

1. Introduction
1T-TiSe2 is a transition metal dichalcogenide (TMD) material. Previous ARPES reports has elucidated that its
electronic structure is primarily composed of the Se-4p valence band located at the A point and the Ti-3d conduction band at
the L point of the Brillouin zone, respectively. Notably, below TC 200 K, TiSe2 undergoes a charge density wave (CDW)
phase transition characterized by a 2 × 2 × 2 ordering. Such transition leads to a backfolding of the Se 4p band to the L
point[1,2].
In this study, we delve into the dispersion of the Ti-3d band at the L point above EF using TR-ARPES. Our
observations reveal the band renormalization and an increase in effective mass after excitation. By correlating the effective
mass with pump fluence, we found that the CDW phase can be completely destroyed beyond a certain fluence threshold. As
the fluence increase, the effective mass becomes heavier, indicating the greater disturbance and longer recovery time of
CDW phase. Such transient melting of CDW order was previous reported in optical pump-probe measurements on rare-earth
tritellurides material LaTe3, where the oscillation of the CDW order persists only at low fluence without complete
breakdown[3]. Consequently, we declare that analyzing the evolution of the effective mass of Ti-3d electron pocket as afunction of pump fluence provides deeper insights into the intricate interactions in 1T-TiSe2.

2. Figures

Figure 1. (a) Brillouin zone of 1T-TiSe2 with high symmetry labels. (b) Schematic disgram of the band structure in CDW phase. (c)Second-derivative band dispersion at L-point after excitation with fluence of 0.09 mJ/cm2. (d) The fluence-dependent spectra along A-L
direction at timezero measured with F = 0.07 mJ/cm2 to 1.0 mJ/cm2. The solid lines indicates the fitting curves. (e) TR-ARPES spectra along
A-L direction in equilibrium and after excitation with 800 nm pump pulses at 0.2 mJ/cm2 fluence.

3. Equations=
4. References[1] Huber, M. et al. “Mapping the dispersion of the occupied and unoccupied band structure in photoexcited 1T-TiSe2”. Journal of Physics
and Chemistry of Solids 168, 110740 (2022).1[2] C.Monney et al, “Dramatic effective mass reduction driven by strong electronic correlations” . Europhysics Letters ,92(2010) 47003.
[3] Dolgirev, P. E. et al. “ Amplitude dynamics of the charge density wave in LaTe 3 : Theoretical description of pump-probe experiments. ”.
Physical Review B 101 (2020).

NYCU-TUAT-UY Symposium 2023

POS. 27

Ultrafast dynamics of SrCd2Sb2 and SrCd2As2 single
crystals using optical pump-probe spectroscopy
Nidhi Puri1 †, Jiunn-Yuan Lin1, Chih-Wei Luo2,3,4,5,6, Chien-Ming Tu2, Wen-Yen Tzeng2, Chi-Chen Tsai1,
Jiun-Haw Chu3, Cheng-Chien Chen7
1
Institute of Physics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
3
Department of Physics, University of Washington, Seattle, Washington 98195, USA
4
Taiwan Consortium of Emergent Crystalline Materials (TCECM), National Science and Technology Council, Taiwan.
5
Institute of Physics and Center for Emergent Functional Matter Science, National Yang Ming Chiao Tung University, Hsinchu, 30010,
Taiwan6
National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan.
7
University of Alabama at Birmingham, Birmingham, Alabama, US
2Author e-mail address†: nidhi.puri@nycu.edu.tw

Abstract: Topological insulators (TIs) represent a novel category of quantum materials characterized by theirinsulating properties in the bulk, accompanied by robust gapless surface states known as topological surface states(TSS). These surface states exhibit a unique behavior wherein the spin direction of electrons is locked
perpendicular to their momentum due to the strong influence of spin-orbit interaction [1,2]. TIs have gained
significant attention for their potential to uncover fascinating physics and to pave the way for various applications
in fields like optoelectronics, spintronics, and quantum computing [1-4]. In this context, the present study utilizes
AB2X2 type SrCd2Sb2 single crystals to study the ultrafast dynamics of carriers and phonons to gain insight into
critical changes in crystal structure. Here, a powerful technique of optical pump-probe (OP-OP) spectroscopy (Fig.
1a) in studying dynamic electronic processes, was employed to investigate the response of as-synthesized
SrCd2Sb2 and SrCd2As2 single crystals under ultrafast laser excitation. To obtain the best-fit to ΔR/R curve, a triexponential function has been used and the parameters have been tabulated in the Fig. 1 below. The significant
observations from the OP-OP measurements include, (i) absence of sub-ps 𝜏1 decay component in SrCd2Sb2, (ii)appearance of ~10 ps decay term (𝜏3 ) for SrCd2Sb2, and (iii) the change of sign for the amplitude (𝐴2 ) of several
ps 𝜏2 decay term. The results revealed contrast ultrafast dynamics between SrCd 2As2 and SrCd2Sb2 thereby
implying that SrCd2As2 and SrCd2Sb2 have distinct electronic structures near the band edge. The transientreflectivity (ΔR/R) curve (Fig. 1b) shows a sharp rise followed by a slow decay. A detailed analysis on the current
results will provide deeper understanding on the underlying physics of the electronic structure of SrCd2Sb2 single
crystals.
We are grateful to NSTC of Taiwan and AFOSR of US for supporting this project (NSTC-110-2124-M-A49-007MY3).

Fig. 1. The transient reflectivity (ΔR/R) curves obtained from the OP-OP spectroscopy. The table on the right side shows the fitting
parameters estimated from the tri-exponential fitting function.

References[1] J.E. Moore, “The birth of topological insulators”, Nature, 194-198, 464 (2010).
[2] M.Z. Hasan, C.L. Kane, “Topological insulators”, Rev. Mod. Phys. 3045-3067, 82 (2010).
[3] C.W. Luo et al, “Snapshots of dirac fermions near the dirac point in topological insulators”, Nano Lett., 5797-5802, 13 (2013).
[4] C.-M. Tu et al., “Manifestation of a second Dirac surface state and bulk bands in THz radiation from topological insulators”, Sci.
Rep., 14128, 5 (2015).

NYCU-TUAT-UY Symposium 2023

POS. 28

Temperature dependent ultrafast dynamics of topologicalmaterial EuCd2Sb2
Chi-Chen Tsai1†, Jiunn-Yuan Lin1, Jiun-Haw Chu3, Cheng-Chien Chen7, Nidhi Puri1, Yu-Sheng Kuo1,
Wen-Yen Tzeng2, Chien-Ming Tu2, Chih-Wei Luo2,3,4,5,6
1Institute of Physics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
2 Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
3 Department of Physics, University of Washington, Seattle, Washington 98195, USA
4Taiwan Consortium of Emergent Crystalline Materials (TCECM), National Science and Technology Council, Taiwan.
5Institute of Physics and Center for Emergent Functional Matter Science, National Yang Ming Chiao Tung University, Hsinchu, 30010,
Taiwan.
6National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan.
7University of Alabama at Birmingham, Birmingham, Alabama, US
Author e-mail address†: godtsai310195@gmail.com

Abstract: Topological materials (TMs) have recently gained attention due to their potential physical properties
for applications in spintronics devices and quantum computing [1-4]. Topological insulators (TIs), one kind ofTMs, exhibit conducting surface states protected by time-reversal symmetry, and the gapless surface states are
resulted from band inversion as well as spin-orbit coupling. In this study, we report on the ultrafast carrier
dynamics of TM EuCd2Sb2 single crystals by two-color optical pump-optical probe (OP-OP) technique (Fig. 1a).
A long-cavity Ti:sapphire oscillator (XL300, FemtoLaser Inc.) was employed to generate 400-nm optical pulses
for pump and 800-nm optical pulses for probe beam. The time-domain traces of transient reflectivity (ΔR/R) of
the probe pulses were recorded in the temperature range of 2-300 K. TheΔR/R curve for 300 K and 2 K (Fig.
1b) shows negative and positive signal, respectively. In addition, we also applied a magnetic field of 6 T
horizontal to the c-axis of the sample and performed the OP-OP measurements in the temperature range of 2-30
K. The detailed analysis of these results will be carried out to have a deeper understanding on the ultrafast
dynamics of EuCd2Sb2 single crystals.
We are grateful to NSTC of Taiwan and AFOSR of US for supporting this project (NSTC-110-2124-M-A49007-MY3).

(a)

(b)

Fig. 1.(a) Schematic diagram for OP-OP system (b) The transient reflectivity curve for EuCd2Sb2 result at room temperature and 2 K in time
domain.

References[1] J-M. DeStefano, L-L Wang, Phys. Rev. B 103, 115207 (2021).
[2] J.E. Moore, “The birth of topological insulators”, Nature, 194-198, 464 (2010).
[3] M.Z. Hasan, C.L. Kane, “Topological insulators”, Rev. Mod. Phys. 3045-3067, 82 (2010).
[4] M. Z. Hasan and J. E. Moore, “Three-Dimensional Topological Insulators”, Ann. Rev. Condensed Matter Physics 2, 55-78 (2011).

NYCU-TUAT-UY Symposium 2023

POS. 29

Ultrafast carrier dynamics of SWCNT under existence ofamino acids
Chia-Hung Lin , Atsushi Yabushita , Chih-Shian Wang
Department of Electrophysics, National Yang Ming Chiao Tung University, Science Building III, No 1001, University Rd., Hsinchu 300,
TaiwanAuthor e-mail address: lsps94161@gmail.com

Abstract: In this work, the home-made NOPA (Non-collinear optical parametric amplifier)system is used to study the carrier dynamics of single-walled carbon nanotubes and aminoacid solutions. Through the NOPA system, the visible probe light of about 10 femtosecond
pulses and the multichannel lock-in amplifier are used to analyze the ultrafast transientabsorption spectrum detected in the visible light band (500nm～700nm). Carrier dynamics ofcarbon nanotubes mixed with amino acids.
Global fitting analysis estimates the two times of in-band relaxation and inter-band relaxation
to be 50fs~100fs and 500fs~1ps, respectively. The analysis results show that addition ofamino acids change the relaxation time of the carriers in the SWCNTs reflecting initialinteraction mechanism between SWCNTs and amino acids.
1. Introduction
In the non-covalent modification method, dispersants such as surfactants, polymers, proteins, etc., havebeen widely studied in the aqueous dispersion of carbon nanotubes. However, these studies mainly focus on a
few dispersants, and a deeper understanding of the dispersing properties and stabilizing effects of other aminoacids is still lacking. In addition, amino acids are an elementary unit for composing proteins and determine theirchemical properties, thus, this work shed light on the interactions between CNTs and proteins in femtosecond
region, to understand the biological effects CNTs of and lead to potential biological applications.
2. Materials and methods
The laser system used in this experiment is the NOPA, after adjusting the pulse compression, by the secondharmonic generation frequency-resolved optical gating can finally compress the pulse width to less than
10fs[1,2]. The schematic diagram of the system is shown in Figure 1.

Fig. 1. NOPA system

3. Experimental results
Using global fitting analysis, the Figure 2-5 shows the Transient absorption (TA) rate changes of the four
sample in the long-time range of 672nm. The black line is the absorptivity change of the actual measurement,
and the red line is the fitting result:Fig.2 . SWCNT

Fig.3 . SWCNT + Arginine

Fig.4 . SWCNT + Histidine

Fig.5 . SWCNT + Lysine

4. Conclusion
In this experiment, two kinds of relaxation times are estimated to be about 50fs~100fs and 500fs~1ps,
representing the intra-band relaxation time and inter-band relaxation time respectively.
5. Reference[1] T. Kobayashi, A. Baltuska, Meas. Sci. Technol. 13, 1671-1682 (2002).
[2] C. J. Bardeen, Q. Wang, C. V. Shank, Phys.Rev. Lett. 75, 3410 (1995).

NYCU-TUAT-UY Symposium 2023

POS. 30

Ultrafast dynamics of carbon nanotubes with different chiralities
Hsuan Yu Ou, Sai Shiwen, Atsushi Yabushita
Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 300, Taiwan, ROC
E-mail: hsuanyu.sc11@nycu.edu.tw

1.

Abstract: Ultrafast spectroscopy was employed to investigate purified and unpurified singlewalled carbon nanotubes (SWCNTs), revealing three relaxation processes with rates of 10, 2,
and 0.5 ps−1, respectively. The fastest one originated from intraband relaxation in the electronic
excited state, while the other two involved interband relaxation, returning electrons to theground state. The unpurified sample exhibited molecular intermolecular vibrational energy
transfer.
Introduction

Single-wall carbon nanotubes (SWCNTs) [1] have garnered significant attention due to their properties lying
between those of fullerene and graphene. Their high tensile strength makes them suitable for applications likearmor and composite materials, while their exceptional thermal conductivity offers advantages in fields such as
space elevators. The electrical conductivity of SWCNTs is influenced by their chirality (n, m), and spectroscopic
techniques can characterize this chirality. Time-resolved studies employing femtosecond pulses of 10 fs
investigate photoexcitation, exciton formation, and dynamics. Ultrafast absorption spectroscopy unveils electronic
and RBM dynamics in SWCNTs of varying chiralities. This research deepens our comprehension of SWCNT
properties and optical behavior, holding significant implications for future applications and advancements inbiosensing [2].
2.

SWCNT samples

Commercially available (6,5) single-walled carbon nanotubes (SWCNTs) containing other chiralities were used,and no further purification was conducted. In the experiment, SWCNTs were dispersed in water containing
sodium dodecyl sulfate (SDS) using ultrasonication, followed by centrifugation in a high-speed centrifuge.
Sodium dodecyl sulfonate (SDS) was used for separation, and SWCNTs were subjected to chirality sorting
using the JASCO chromNAV system. Ultimately, purified (6,5) SWCNT samples were obtained and subjected
to optical measurements in water containing sodium cholate (SC).
3. Results and discussion
We conducted spectral measurements on two types of nanotube samples, non-purified and purified, with afocus on the spectral region of 612–630 nm (see Fig. 1). In the 612–630 nm range, the RBM of the non-purified
sample exhibited an upward trend (see Figure 1a). This change could arise from two mechanisms. The firstpossibility is the overlap of RBMs with different frequencies. However, the observed traces are unlikely to reflect
such overlap. The second possibility is energy transfer between different chiralities, but considering the diameter
differences of the samples, a single nanotube cannot contain both chiralities simultaneously. Therefore, we
attribute the observed upward shift to energy transfer between nanotubes of different chiralities. In the nonpurified sample, the RBM frequency appears to approach that of the (6,4) chirality, while it remains stable in the
purified sample. Simultaneously, for the non-purified sample, the transient absorption signal in the 612–630 nm
region exhibited positive (negative) values, reflecting induced absorption from the electronically excited state(ground-state bleaching) (see Fig. 2).

Fig. 1. Spectrogram traces of the (a)non-purified (b) purified

Fig. 2. Transient absorption spectra ΔA(λ, t) for non-purified

4. References[1] S. Iijima, T. Ichihashi, Single-shell carbon nanotubes of 1-nm diameter, Nature 363 (1993) 603–605.
[2] C.M. Tîlmaciu, M.C. Morris, Carbon nanotube biosensors, Front. Chem. 3 (2015) 59

NYCU-TUAT-UY Symposium 2023

POS. 31Ultrafast dynamics of CongoRed under adsorption
ChiaYun Cheng, WeiXiang Huang, Atsushi Yabushita
National Yang Ming Chiao Tung University Department of Electronphysics
ellena8973@gmail.com

Abstract: Using Ultraviolet pump and white light probe (UPWP) system, a harmonic pulse
centered at 400nm wavelength is used to make the sample go from the ground state to the excitedstate, and use broadband WLC pulse detection light to analyze the ultrafast kinetics of the Congo
red sample. The clear and complete record of the ultrafast dynamic response detected in the
wave band (500~750 nm) is used to calculate the decay spectrum (DAS) and its lifetime. We
observed that at higher laser power, the decay time is shorter.
1.

Material and methods

Congo red (CR) studied in this work, is known to bind to amyloid proteins and thought to be useful forcharacterization of amyloid formation in Alzheimer patients [1]. Using the system described below, we have
performed ultrafast spectroscopy for an aqueous solution of CR (CR-H2O) and a water dispersed solution of CR
adsorbed on a particle of hydroxyl apatite (CR-HA).
Using Ultraviolet pump and white light probe (UPWP) as Fig. 1. The light source emits near-infrared (NIR)
pulses, which are then split into two pulses by a beam splitter. The higher intensity NIR pulse is focused on βBaB2O4 (BBO crystal) to generate a 400 nm second harmonic (SH) pulse, which is used to excite the sample
from the ground state to the excited state. The lower intensity NIR pulse is focused on a 2mm thick sapphire plate,
producing a wideband white-light continuum pulse (WLC) due to focusing effects and third-order susceptibility.
A short-pass filter is used to eliminate spectral components above 750nm, and this WLC pulse is used as the
probing pulse. After passing through the sample, the light is dispersed through an optical fiber and coupled into a
photodiode array (PDA) camera. The excitation pulses are modulated at a frequency of 2.5 kHz using an opticalchopper. The spectrum obtained from the PDA camera observes the difference in absorption between the presence
and absence of the excited sample.

2. Results and discussion
Ｗe conducted ten cycles of scans to obtain the average measurement, generating a substantial amount of dataof variation in transmittance ∆𝑻. By analyzing this data, we obtained transient absorption ∆𝑨, which was thensubjected to global fitting to determine the decay time then calculate the average decay time τ for each laser power.
Comparing the results between CR-HA and CR-H2O samples, we observed that at higher laser power, the decay
time was shorter. This could be attributed to the higher power laser providing more energy, accelerating theinteraction between light and matter, resulting in faster generation of photoproducts. Furthermore, due to the closer
proximity of CR-HA molecules adsorbed on Hydroxyapatite, there might be an enhancement of accelerated
photopolymerization and photoproduct generation [2,3]. In contrast in the CR-H2O sample, where the molecules
are more spaced apart, the generation of photoproducts is slower. Overall, we noted a negative correlation between
laser power and decay time.
3. References[1] Styren, S. D.; Hamilton, R. L.; Styren, G. C.; Klunk, W. E., (2000), A ﬂuorescent derivative of Congo red: A
novel histochemical stain for alzheimer’s disease pathology. J. Histochem. Cytochem. 48(9), 1223–1232.
[2] Heyne, B. (2016). Self-assembly of organic dyes in supramolecular aggregates. Photochemical &Photobiological Sciences, 15, 1103-1114.
[2] Chen, Z., Lohr, A., Saha-Möller, C. R., & Würthner, F. (2009). Self-assembled π-stacks of functional dyes insolution: structural and thermodynamic features. Chemical Society Reviews, 38(2), 564-584.