bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of Artificial Neural Networks for Hartman Sensor Lenslet Centroid Estimation
Authors: Montera Dennis A. , Welsh Byron M. , Roggemann Michael C. , Ruck Dennis W.
Published: February 2023

The resolution of ground based telescopes is limited by the random wavefront aberrations caused by atmospheric turbulence [1]. Adaptive optics systems, which compensate for atmospheric effects, have been shown to improve the resolution of these telescopes [2]. The purpose of an adaptive optics system is to remove the atmospheric induced aberrations from an incident optical wavefront. This removal is accomplished by measuring the incident aberrations and removing them using a deformable mirror. The compensation is degraded by the effects of additive noise in the wavefront sensor (WFS), system time delays, and the possibility of a spatial separation between the object of interest and the beacon used to measure the incident wavefront. While an optimal wavefront reconstruction algorithm, such as the minimum variance reconstructor, can be derived based on statistical knowledge of the atmosphere, noise and other random effects in the adaptive optics system cause the actual performance of this reconstructor to be limited by imperfect knowledge of several key parameters [3, 4, 5]. These parameters include both atmospheric and system parameters. The key atmospheric parameters include the Fried coherence length [6], r0, the

C
n
2

profile, and the wind speed profile. The key system parameter is the WFS mean square slope measurement error. The most common form of WFS used in adaptive optics is the Hartmann WFS. In this paper we look at reducing the slope measurement error in a Hartmann WFS by improving the subaperture centroid estimation. In particular, neural networks are trained to estimate the subaperture centroid location, and the results are compared to those obtained using a conventional centroid estimator.
An Optical Ultrahigh Resolution Spectrograph with the Adaptive Optics
Authors: Ge J. , Jacobsen B. , Angel J.R.P. , Woolfv N. , Black J. H. , Lloyd-Hart M. , Gray P. , Fugate R. Q.
Published: February 2023

A prototype optical wavelength ultrahigh resolution echelle cross-dispersed spectrograph has been tested at the Starfire Optical Range (SOR) 1.5 m telescope (Woolf et al. 1995; Ge et al. 1996). To our knowledge this is the first high resolution spectrograph to take advantage of the diffraction limited images produced by an adaptive optics system. Because of the sharpened images produced by the adaptive optics at visible wavelength, about r0/D ~ 1/15 in the seeing-dominant domain, the narrow slits necessary for high resolution can be used without a large loss of light. This is a great advantage when compared with conventional high resolution spectrographs (e.g. Lambert et al. 1990; Diego et al. 1995). In addition, the smaller image widths inherent with the adaptive optics system allow the orders to be spaced closer together on the chip, allowing more orders to be observed simultaneously.
Roles for Phase Diversity in Compensated Imaging
Authors: Paxman Richard G.
Published: February 2023

Astronomers have long known that the resolution in ground-based astronomy is almost always limited by aberrations introduced by the atmosphere. Over the years, researchers have developed a variety of clever pre- and post-detection approaches for correcting these effects. A strong argument can be made for pre-detection correction. It can be shown that the Modulation Transfer Function (MTF) will achieve a maximum at each spatial frequency when the system is unaberrated [1]. Aberrations can only modulate object spatial-frequency information to reduced levels. This modulation could be perfectly inverted in the absence of noise. However, detection of the imagery always introduces noise and inversion schemes result in noise amplification. Therefore, when it can be successfully accomplished, pre-detection correction is preferable to post-detection correction with regard to signal-to-noise ratio.
Second-Order Statistics of the Performance of the Starfire Optical Range Adaptive Optics System
Authors: Johnston Dustin C. , Brown James M. , Christou Julian C. , Ellerbroek Brent L. , Fugate Robert Q. , Oliker Michael D. , Spinhirne James M.
Published: February 2023

Early in the development of adaptive optics technology, the goal was to obtain good instantaneous results, i.e., well-compensated short-exposure images. The next goal was expressed in terms of average results, for example, acquiring good long-exposure images. The next logical step in characterizing and improving adaptive optics (AO) system performance is to investigate the second-order statistics. For example, we are interested not only in the average point spread function (PSF), but also the variance of the PSF. Depending on the application, we may be interested in the second-order statistics of other widely used measures of AO system performance such as the optical transfer function (OTF), Strehl ratio, image width, and encircled energy. The variance of the PSF/OTF is of interest when post-processing AO-compensated images.1 The variance of the OTF appears explicitly in the denominator of the image spectrum signal-to-noise ratio.2 Some researchers have suggested that AO may be useful in the area of optical communications to deep space probes.3 In such an application, one is interested in the statistical variation of the coupling efficiency of the compensated beam to an optical receiver and the frequency, duration, and distribution of signal excursions below threshold levels.4
Temporal Characteristics and Modelling of Atmospherically-Distorted Wavefront Slopes
Authors: McGaughey Donald , Aitken George J. M.
Published: February 2023

The wavefronts distorted by a Kolmogorov turbulent atmosphere are fractal surfaces [1] and have the properties of fractional Brownian motion (FBM) with a self-similarity parameter of 5/6. Such a FBM process is nonstationary and has a power-law spectrum with spectral index -8/3. In an adaptive optics system a Shack-Hartmann (SH) wavefront sensor (WFS) delivers the time series of wavefront (WF) slopes measured at each lenslet subaperture. While the FBM wavefront exhibits persistence, and consequently has predictability, the derivatives or slopes of this FBM process are antipersistent [2] with spectral index -2/3. This means that the WF slopes would have limited predictability at least by conventional mean-square prediction methods. Thus the adaptive optics (AO) control strategy that treats WF slopes as an unpredictable random walk process would seem justified. Within a closed loop system the difference between the incident wavefront and the correction by the deformable mirror is equivalent to a differentiation or increments process because of the loop delay, in which case the wavefront sensor gives essentially the second derivative. The second derivative process of FBM is also antipersistent.
Atmospheric Characterization for Adaptive Optics at the Keck Telescope
Authors: Chanan Gary , Crnkovic Romana , Dekens Frank
Published: February 2023

la Perpendicular segment-to-segment tilt correlations for the Keck Telescope, caused by atmospheric turbulence. Here, “perpendicular” refers to that tilt component perpendicular to the line connecting the segment centers. Horizontal axis is separation in units of the segment diameter (1.64 m). The full 10 meter baseline was not reached because of limitations on the detector size. Sampling was at 91 Hz for 164 seconds. Tilts were corrected for telescope drift by removing global linear trend. Theoretical curves (after Takato and Yamaguchi 1995) are labeled with assumed outer scale; curve marked “Kolmogorov” is for infinite outer scale. Data points are from a representative run; a series of 28 runs from May 1994 and August 1995 shows similar results, with the average value of the outer scale less than 200 m.
Evaluation and development of SCIDAR with the aid of 3D propagation code.
Authors: Adcock Miles J. , Klückers Vincent A. , Wooder Nicholas J. , Dainty Christopher
Published: February 2023

SCIDAR (Scintillation Distance And Ranging) is used to determine the height and strength of optically turbulent layers in the atmosphere. One use of this information is in adaptive optics, both in the design of a system and in its regular operation. The technique of was first proposed by Vernin and colleagues [1, 2, 3, 4], and further developed by Tyler [5]. This paper evaluates SCIDAR as a method for turbulence profiling, and describes algorithms which have been developed to make it viable. This has been aided by a simulation of the propagation of light through 3D random media.
Measurement of a Non-Kolmogorov Structure Function
Authors: Nicholls Tom , Wooder Nicholas J. , Dainty Christopher
Published: February 2023

The structure function of atmospheric phase fluctuations is defined as follows: A generalised model for the structure function of phase is: ℛ
0
is related to the size of the long-exposure image formed by a large-aperture telescope, while γ
ß
is a parameter which depends on ß and on the precise definition of ℛ
0
The widely-used Kolmogorov model of refractive index fluctuations [1] predicts a value of 11/3 for ß; in this case, with the appropriate definition, ℛ0 is equivalent to r0, the Fried parameter [2], Under the Kolmogorov assumption, the parameter r0 entirely describes the time-averaged statistics of the phase fluctuations. A knowledge of r0 can be used, for example, to predict how the energy in the phase fluctuations is distributed between the Zernike modes.
Measurements of the Isoplanatic Angle of the Wavefront Tilt
Authors: Berkefeld Thomas , Glindemann Andreas
Published: February 2023

Investigating the tilt correlation as a function of separation angle, exposure time and aperture, the maximum angular distance between the object and the tip-tilt guide star is determined. This distance can be increased by multiple guide stars.
Deconvolution from Wave-Front Sensing Enhanced with Blind Deconvolution
Authors: Dayton David , Sandven Steve , Gonglewski John
Published: February 2023

INTRODUCTION

Deconvolution from Wave-Front Sensing (DWFS) has been investigated both through laboratory and field experiments as a method to produce high resolution images from ground based telescopes.1,2,3 This technique has sometimes been referred to as Speckle Holography. With this technique a short exposure focal plane image is recorded simultaneously with an estimate of the atmospheric wave-front. The wave-front estimate is used to calculate an optical transfer function (OTF) for the atmosphere. This OTF estimate is then used in a deconvolution algorithm to correct the focal plane image. A synoptic sketch of a DWFS instrument is shown in figure 1.
Simulation Of Adaptive Optics Improvement On Laser Communication Link Performance
Authors: Rosenberg Brian , Barbier Pierre R.
Published: February 2023

Terrestrial laser communication systems may be limited in their performance by atmospheric turbulence, which distorts the wavefront of a propagating laser beam [1]. At low turbulence levels a laser communication link is limited by atmospheric beam wander. This effect can be corrected by implementing an adaptive pointing system at the transmitter or by increasing the beam size at the receiver [2]. At higher turbulence levels the communication link is also limited by atmospheric scintillation, i.e., amplitude and phase distortions, at the receiver. These distortions induce power fading of the optical carrier detected by the receiver, resulting in an increased bit error rate (BER) of the system. The designer of a laser communication system will therefore seek to maximize the energy collected by the receiving photodetector while minimizing variations in this quantity. One approach to this problem is to implement an adaptive optic system to correct wavefront distortions and reduce power fadings. With an eye to astronomic applications, however, adaptive optics is usually designed to improve the Strehl ratio, resulting in greater image quality [3] but not necessarily in power fading improvement. Few comparisons of the Strehl ratio and collected energy (and hence BER) have been performed [4], making it difficult to assess the benefit of adaptive optics on a communication system. In this work we present the result of Monte Carlo simulations of a strongly turbulent atmosphere and compare the improvement on Strehl ratio and collected energy at the receiver of a laser communication link with and without adaptive optics.
Effects of Interface defect on the performance of ZnO/p-Si heterojunction solar cell
Authors: Askari Syed Sadique Anwer , Kumar Manoj , Das Mukul Kumar
Published: February 2023

The study and optimization of emitter zinc oxide/crystalline silicon heterointerface with a focus on recombination has been identified as the most important issue to fully utilize the potential of ZnO/Si heterojunction solar cell [1]. ZnO/Si interface properties are very crucial to the performance of solar cell due to the fact that the interface is located inside the space charge region. Front surface recombination of Si or the interface recombination velocity of ZnO/Si interface is the most important parameter in this simulation that dictates the efficiency of solar cell. It is known that the open circuit voltage (Voc) of the cell with the negative band offset at the absorber/emitter interface may be limited by interface recombination [2].
Silicon Photonic Devices
Authors: Chu Tao
Published: February 2023

Accompanying the rapid developments of the big-data society and the network of the things, novel technologies for constructing high-speed and low-power-consumption data processing and communication systems are highly demanded. Silicon photonic integration is widely regarded as one of the most promising ways in various applications, due to the low-cost and high-density-integration of silicon photonic devices. Many novel photonic devices based on silicon-on-insulator waveguides were developed. Here, some novel silicon photonic devices will be introduced, including silicon digital/analog modulators, wavelength MUX/DeMUX devices of AWG and EDG, Mode MUX/DeMUX devices, polarization controlling devices, and large-scale EO/TO silicon optical switches. [1-5].
Heterogeneous Lasers with Silicon Photonic External Cavity
Authors: Kita Tomohiro , Takei Shotaro , Matsumoto Atsushi , Yamamoto Naokatsu , Yamada Hirohito
Published: February 2023

Presently, silicon photonics is receiving considerable attention because it provides a promising platform for fabrication of highly integrated photonic devices. In addition, silicon photonic devices can be fabricated using the mature fabrication technologies of electric integrated circuits. We focused on an integrated light source and developed wavelength tunable lasers using silicon photonic technologies. The narrow spectral linewidth heterogeneous laser diode with high optical output power was realized for optical digital coherent communication systems[1]. The recent studies for expanding the availability of heterogeneous lasers will be presented.
Fabrication of Monolithic InGaAlAs/InAlAs MQW-based Polarization Controller
Authors: Kazi M. , Ghosh S. , Sodabanlu H. , Sugiyama M. , Tanemura T. , Nakano Y.
Published: February 2023

Polarization controllers are becoming increasingly important for various applications, including adaptive polarization stabilization and Stokes-vector modulation in optical networks, RF photonics, bio-imaging and sensing, and quantum optics. In order to reduce the size and cost of conventional bulky optical components, various types of integrated polarization controllers have been researched over the years. Among others, simple straight-line scheme consisting of integrated polarization converter (PC) and polarization- dependent phase shifter (PD-PS) has been proposed and implemented on InP platforms [1-3]. These previous demonstrations, however, employed identical epitaxial layers for both PC and PD-PS sections, which has limited the performance.
Optical Spectroscopy of Individual Nano-materials with Defined Atomic Structure
Authors: Liu Kaihui
Published: February 2023

When the characteristic length of a material shrink to 1 nm scale, many distinct physical phenomena, such as quantum confinement, enhanced many-body interactions, strong van der Waals inter-material couplings and ultrafast charge separation, will appear. To investigate the related fascinating low-dimensional physics, we need a tool to quantitatively link the atomic structures to the physical properties of these very small nano-materials. In this talk, I will introduce our recently developed in-situ TEM + high-sensitive ultrafast nanooptics technique, which combines capability of structural characterization in TEM and property characterization in nanooptics on the same individual nano-materials. Several examples of using this technique to study the 1D carbon nanotube system and 2D atomic layered systems will be demonstrated.
250 mW output power operation of GaAs-based THz quantum cascade lasers
Authors: Lin° Tsung-Tse , Terashima Wataru , Hirayama Hideki
Published: February 2023

THz quantum cascade lasers (QCLs) [1,2] are promising high output power semiconductor THz sources to over Watt order peak power [3] with narrow bandwidth. It is still quite limited for the THz applications caused by the large cryogenic system and low duty cycle with low output power at high operation temperature. Output power is one of the most critical parameters for real applications. We demonstrated a 77 K liquid nitrogen Dewar condenser as a compromised compact portable THz source unit with our fabricated QCLs. They showed a stable few ten mW peak power with sub mW average power operation. Analysis the temperature performance of structures by Non-Equilibrium Green’s Function (NEGF) method are discussed. The improvement of the active region and waveguide fabrication will also be discussed for high output power operation in order to exhibit the best performance of the compact 77 K Dewar system.
High Purity Synthesis of (6,4) Single-Walled Carbon Nanotube by Surface State Control of Co Catalyst
Authors: Xu Bin , Kaneko Toshiro , Shibuta Yasushi , Kato Toshiaki
Published: February 2023

Single-walled carbon nanotubes (SWNTs) have many outstanding properties due to the unique 1-dimensional structure. Especially, fabrication of the high performance device utilizing the intriguing opt-electronic property is regarded as a very promising output. However, the opt-electronic property is decided by the helicity of graphene wrapping, which is defined as SWNTs chirality, making the chirality control of SWNTs a very critical issue. Towards this goal, many researches about the precise control of catalyst are reported and the effects of catalyst size [1] and crystal structure [2] are well studied. On the other hand, the correlation between catalyst surface condition and chirality is seldom being studied, and the details still remain unclear. In this study, systematic investigations are carried out aiming for the elucidation of the correlation between SWNTs chirality and catalyst surface condition.
Room-temperature single photon emission from micron-long air-suspended carbon nanotubes
Authors: Ishii A. , Uda T. , Kato Y. K.
Published: February 2023

Carbon nanotubes have great potential for single photon sources as they have stable exciton states even at room temperature and their emission wavelengths cover the telecommunication bands. In recent years, single photon emission from carbon nanotubes has been achieved by creating localized states of excitons [1]. In contrast to such an approach, here we utilize mobile excitons and show that single photons can be generated at room temperature in air-suspended carbon nanotubes with lengths of several microns. We perform photoluminescence microscopy on as-grown air-suspended carbon nanotubes in order to determine their chirality and suspended length. Photon correlation measurements are performed on nanotube emission at room temperature using a Hanbury-Brown-Twiss setup with InGaAs/InP single photon detectors. We observe antibunching with a clear excitation power dependence, where we obtain g(2)(0) value less than 0.5 at low excitation powers (Fig. 1), indicating single photon generation. We show such g(2)(0) data with different chiralities and suspended lengths, and the effects of long exciton diffusion lengths and efficient exciton-exciton annihilation [2] on single photon generation processes are discussed.
Near-infrared up-conversion photoluminescence imaging of carbon nanotubes in mice tissues
Authors: Okudaira Saki , Iizumi Yoko , Yudasaka Masako , Okazaki Toshiya , Matsuda Kazunari , Miyauchi Yuhei
Published: February 2023

Single-walled carbon nanotubes (SWNTs) have been considered as promising luminescent probes for deep-tissue bioimaging because of their intrinsic photoluminescence in the near infrared wavelength range of ~1000-1300 nm called NIR-II [1, 2]. The near infrared light readily penetrates into highly scattering media such as biological tissues; this enables photoluminescence imaging of deep inside of them. However, it is necessary to use Stokes photoluminscence (here after, referred to as PL) at longer wavelengths than ~1100 nm to avoid autofluorescence from the biological tissues, and standard Si-based detectors cannot be used in this wavelength range. Recently, efficient up- conversion photoluminescence (UCPL) of SWNTs has been discovered [3]. The UCPL phenomena enable SWNTs excited at wavelengths longer than ~1050-1200 nm to emit PL shorter than 1000 nm in which standard Si-based detectors have finite sensitivity. The availability of the UCPL thus drastically enhances the usefulness of SWNTs as luminescent probes in their bioimaging applications.
Anisotropic Permittivities and Transmittance of Double Layer Graphene
Authors: Zhang Jun-Fu , Li Jia-Han , Sheu Tony Wen-Hann
Published: February 2023

Graphene is a two dimensional material consisted of honeycomb carbon lattices. Comparing to pure graphene, bilayer graphene is taking special interest due to the interlayer interactions. The interlayer coupling has the influences on the electronic and optical properties, which has crucial characteristics distinct from graphite. Ebernil et al. [1] reported that the single layer graphene has red-shifted surface plasmon modes from graphite at 4.7 eV and 14.6 eV. It illustrated that the dielectric function of graphene distinct from graphite. In this work, the permittivities of double layer graphene are numerically simulated using Density Functional Theory (DFT) method. Also, the transmittance of SiO2 substrate model, surface conductivity approach of graphene model, and DFT model are compared.
Flexible Film Metamaterial for a thin THz-Wave Phase Shifter
Authors: Han Zhengli , Tokizane Yu , Nawata Kouji , Notake Takashi , Takida Yuma , Minamide Hiroaki
Published: February 2023

Thin terahertz (THz) -wave optical components are essentially required in integrated THz-wave spectroscopy and imaging systems [1,2]. Generally, not only transmission in amplitude but also phase control are significant on manipulations of wave propagation. In this paper, we report a thin THz-wave phase shifter demonstrated by flexible film metamaterial with high transmission. The device design has two parts, where one works as a phase shifter of 1/4 π and the other works as the reference for the phase shifter. Metamaterial unit structure employs double-layer split ring resonators (SRRs) both for the two parts to obtain the relative phase difference of 1/4 π while keeping the same transmission coefficient of 0.82. The phase shifter also holds the property of polarization independence due to the four-fold symmetry on the SRR structure. The device is developed by photolithography and wet etching techniques with flexible polymer film used as the substrate.
Long distance Terahertz pulse propagation through atmosphere
Authors: Jeon Tae-In
Published: February 2023

Recently, there have been studies of broadband coherent THz pulse propagation under atmospheric weather conditions [1], which provides information for important applications in the atmosphere. In this study, the THz pulses were measured through a 159 m and 883 m distances for which the THz pulses propagated in an outdoor atmosphere with different water vapor density (WVD). The total round trip paths between the transmitter and receiver chips were 186 m and 910 m, which are approximately equal to 52 and 255 round-trips of the circulating 50 fs optical pulse within the mode-locked ring laser, thereby, giving sampling pulses delayed by 52 and 255 pulses down the pulse train from the excitation pulses, respectively. The time shift of the THz pulses was proportional to the WVD. Figure 1 shows the transmitted THz pulses through 186 m and 910 m with different WVDs. The THz pulse delays due to the distance and WVD with respect to the first maximum of the pulse. Finally, the time shift of the THz pulses of the 186- and 910-m distance, for which the outdoor propagation distances are 159 and 883 m with including 27 m indoor propagation distance for both measurements, can be measured as a function of WVD. THz long path WVD studies are necessary to investigate the proposed applications in the atmosphere such as THz communications and monitoring for pollutants and dangerous gases.
GaAsP microelectromechanical beam structures for terahertz bolometer applications
Authors: Qiu Boqi , Zhang Ya , Hosono Suguru , Akahane Koichi , Nagai Naomi , Hirakawa Kazuhiko
Published: February 2023

We reported a room temperature, all electrical driving and detecting, very sensitive thermometer using a GaAs doubly clamped microelectromechanical (MEMS) beam resonator for bolometer applications [1]. When the MEMS beam is heated by radiation, its resonance frequency is shifted by a temperature rise and the signal is detected by the piezoelectric effect [2]. Increasing the quality factor (Q) of the mechanical resonance is advantageous for improving performance of the MEMS bolometer. It was reported that introduction of tensile strain induced by lattice mismatch between GaNAs and GaAs improves the Q-factor of the MEMS resonators by 30 times, when compared with that of unstrained GaAs resonators, and that the resonance frequency is significantly enhanced [3]. However, since nitrogen acts as deep levels in GaAs, it is very difficult to create a conductive layer in the GaAs MEMS beam and form piezoelectric capacitors to realize electrical driving and detection. Therefore, in this work, we introduced phosphorus, instead of nitrogen, to induce a preloaded tensile strain in the MEMS beam and investigated how the tensile strain influence the behavior.
Luminescence of ZnO excited by single intense picosecond terahertz pulse
Authors: Sun Xingyu , Nagai Masaya , Ashida Masaaki , Isoyama Goro
Published: February 2023

Field–sensitive nonlinear phenomena in semiconductors beyond the conventional perturbation theory have been investigated recently using extremely intense terahertz pulses. This year spring, we reported the anomalous luminescence under the irradiation of the THz free electron laser (THz-FEL) pulses[1]. The results, strong excitation frequency- and power-dependences of the luminescence from ZnO nanoparticles and surrounding nitrogen molecules, reflected the kinetic energy and trajectory of electrons outside the nanoparticles, which provided a new excitation path. However, one THz-FEL macropulse consists of about 100 FEL micropulses separated at 37 ns intervals (27 MHz repetition), which complicates the luminescence via undesired charge build-up on the nanoparticles.
Analytical formulation for field enhancement of gold bipyramids and hemispherically capped cylinders for application in two-photon luminescence and scattering
Authors: Chon James W. M.
Published: February 2023

Recent advances in two-photon excited photoluminescence of plasmonic gold nanorods have greatly expanded their application. Shape-controlling of nanorods can enhance a particular photophysical process to tailor needs but its application to two-photon luminescence is yet to be fully developed despite its importance in biolabelling. In particular, bipyramidal gold nanorods have received a large amount of interest as a biolabelling due to highly localised field at their tips, which provide enhancement for emission processes. However, no proper evaluation of geometrical properties of bipyramids such as tip shape, curvature, pentagonal cross section or the waist have been conducted on the field enhancement and peak evolution. Numerical simulations using finite element analysis show that small change in tip radius of curvature can change nonlinear process such as two-photon luminescence (TPL) two to four-fold increase. However, such large increase is not observed in experimental measurement of TPL with respect to tip curvature, indicating that there is fundamental limit to how the field enhancement can influence emission processes.
3D digital holographic semiconductor metrology using Fourier Modal Method
Authors: Park Shin-Woong , Lee Jong Hyun , Kim Hwi
Published: February 2023

Through-focus Scanning Optical Microscope (TSOM) technology, which has been attracting much attention in the field of semiconductor measurement recently, using a conventional optical microscope, collects 2D images at multiple focal positions for creating 3D data space and extracts intensity profile from them. It is a breakthrough technology for the inspection and measurement of a recent complicated 3D structure semiconductor.
Eu-doped on-chip blue-light emitting glass-ceramic waveguides
Authors: Ghosh Subhabrata , Shivakiran Bhaktha B.N.
Published: February 2023

Rare-earth (RE) activated glass-ceramics are two phase composite materials consisting of nanocrystals embedded in amorphous matrix, combining the advantages of optical glasses with the crystal-like environment for RE-ions [1, 2]. Hence, RE-doped transparent glass-ceramic waveguides are widely adopted for integrated optic applications such as on-chip lasers, optical amplifiers etc. [3, 4] because of their narrow and intense emission from 4f-intrashell transition.
Relationship between the Laser Ablated Si Substrate and the Synthesized Materials
Authors: Zhang Dongshi , Sugioka Koji
Published: February 2023

Laser ablation has emerged as a novel method to synthesize a large variety of nanomaterials.1-7 Currently, most works merely focus on the material synthesis using laser ablation technique with little attention to the correlation of the ablated substrates with the synthesized materials. This work is aimed at filling this gap and giving new insights based on laser ablation of single crystal diamond-cubic (dc) (400) Si in air. Polycrystallization is a ubiquitous phenomenon occurring during laser ablation of Si. The polycrystallization rate of the ablated areas increases with increasing the laser powers, which well explains the polycrystalline instinct of the synthesized nanomaterials. Faster cooling rates of the laser-generated molten Si layers over their nucleation rates result in the surface amorphoization. With the aid of laser-generated shock waves, the molten layers together with the newly formed polycrystalline Si materials will be pushed upward in air to solidify amorphous SiOx encapsulated polycrystalline Si composites. This work tends to remind the researchers to pay more attention to the relationship between the ablated surfaces and the collected nanomaterials no matter where the laser ablation is implemented, in either air or liquids or vacuum.
Marangoni Flow in Microfluidics Controlled by Laser Heating of Gold Nanoisland Films
Authors: Namura Kyoko , Suzuki Motofumi
Published: February 2023

Gold nanoparticles absorb light efficiently at their resonant frequency and convert it to heat within several picoseconds. Strong laser irradiation onto those gold nanoparticles enables us to heat the surrounding materials locally and rapidly, which has been reported to be useful for cancer therapy, ultrasonic generation, microfluidic control, and so on. Because the gold nanoparticles can also act as sensing platforms for such as Raman spectroscopy under laser irradiation, development of the microfluidic control method with laser heating of gold nanoparticles is desirable to meet the requirements in lab-on-a-chip devices. Here, we present microfluidic manipulation techniques based on Marangoni effect controlled by laser heating of gold nanoisland films and our most recent outcomes.
Spatiotemporal Control of Crystal Growth of Organic Compounds by Femtosecond Laser Ablation II ~ Laser Energy Dependence~
Authors: Suzuki Daiki , Nakabayashi Seiichiro , Yoshikawa Hiroshi Y
Published: February 2023

Crystallization is crucial for various experimental processes such as purification, crystalline devices, and determination of molecular structures by X-ray/Neutron diffraction. The preparation of crystals with appropriate size and shape is one of the important factors for the success of the above-mentioned processes. In general, researchers try to make such crystals by optimizing the environmental parameters such as temperature, solvents, and additives. On the other hand, our group has recently succeeded in the control of protein crystal growth by directly modifying the local crystal structures via femtosecond laser ablation [1]. Here the key is to induce the spiral growth mode, which is energetically advantageous compared to the spontaneous 2D nucleation growth mode. In the previous account, we reported that this technique can also be applied to crystals of a low-weight organic compound, glycine [2]. In this work, we systematically investigated the dependence of laser energy on the organic crystal growth to explore the optimized condition for the preparation of crystals with desired size and shape.
Harnessing of Rogue Waves for Cascaded Supercontinuum
Authors: He Zhen , Wei Xian Yi , Zhang Wei Li
Published: February 2023

Combined special fibers with different zero dispersion points were proposed to realize random lasing and to stimulate cascaded supercontinuum. Moreover, an external perturbation method was developed to actively control rogue-wave generation of the supercontinuum.
Non-Hermitian Floquet-free analytically solvable time-dependent systems [Invited]
Authors: Ghaemi-Dizicheh Hamed , Ramezani Hamidreza
Published: February 2023

The non-Hermitian models, which are symmetric under parity (P) and time-reversal (T) operators, are the cornerstone for the fabrication of new ultra-sensitive optoelectronic devices. However, providing the gain in such systems usually demands precise control of nonlinear processes, limiting their application. In this paper, to bypass this obstacle, we introduce a class of time-dependent non-Hermitian Hamiltonians (not necessarily Floquet) that can describe a two-level system with temporally modulated on-site potential and couplings. We show that implementing an appropriate non-Unitary gauge transformation converts the original system to an effective one with a balanced gain and loss. This will allow us to derive the evolution of states analytically. Our proposed class of Hamiltonians can be employed in different platforms such as electronic circuits, acoustics, and photonics to design structures with hidden PT-symmetry potentially without imaginary onsite amplification and absorption mechanism to obtain an exceptional point.
Measurement System for Ultraviolet Channel Modeling and Communications
Authors: Arslan Hakan , Dagefu Fikadu , Moore Terrence , Weisman Mike , Drost Robert
Published: February 2023

There has been an increasing interest in ultraviolet (UV) communications as a promising technology for non-line-of-sight (NLOS) networking by exploiting atmospheric scattering at UV wavelengths that enables a unique NLOS UV communication channel. While there has been significant theoretical and simulation-based investigation of the UV channel characteristics, there is limited work in terms of experimental research and validation of the analytical models. In this paper, we present a flexible experimental system for precise UV channel and communications measurements. Specifically, a transceiver system is developed that consists of a gimbal, UV light-emitting-diode array, and photomultiplier tube detector, node synchronization, and LabVIEW-based data acquisition subsystems. Novel techniques to precisely characterize the UV LED array radiation pattern, absolute transmit power, and field of view of the detector are also presented. The utility of the developed system is then demonstrated by performing a variety of experiments including UV channel model validation and steering optimization for UV communication links where the results were in very good agreement with theory and simulation.
Non-resonant cavity for intensity buildup of multiple lasers
Authors: Zeng Yi , Hutzler Nicholas
Published: February 2023

A non-resonant cavity to build up laser intensity is modeled, developed and tested. It can be used for overlapping multiple lasers of different wavelengths, increasing their intensities by over an order of magnitude while maintaining good uniformity. It is simple to set up, has flexible optical characteristics, and is robust against perturbations. The intensity buildup requires no resonances, and the wavelength dependence of the performance is limited only by the mirror coatings. The cavity can be used in applications requiring a spatially-constrained intensity buildup, for example in atomic and molecular traps.
Self-bending Photonic Hook Beam into the Time Domain Based on Phase Change Materials
Authors: Minin Oleg , Minin Igor , Cao Yinghui
Published: February 2023

Tunable optical devices are of great interest as they offer adjustability to their functions. Temporal optics is an evolving new field, and utilizing it are useful as for revolutionize basic research of time-dependent phenomena as for leading toward full optical devices. With increasing focus on ecological compatibility, bio-friendly alternatives are of key subject. Water in its various forms can uniquely open up new physical phenomena and applications in photonics and modern electronics in unique ways. Water droplets freezing on cold surfaces are ubiquitous in nature. We propose and demonstrate the effectual generation of time domain self-bending photonic hook (time-PH) beams by using freezing water droplet. The PH light bend near the shadow surface of the droplet into large curvature and angles superior to a conventional Airy beam. The key properties of the time-PH (length, curvature, beam waist) can be modified flexibly by changing the positions and curvature of the water-ice interface inside the droplet. Due to the modifying internal structure of freezing water droplets in real time, we showcase the dynamical curvature and trajectory control of the time-PH beams. Compare with the traditional methods, our phase-change based materials (water and ice) of the mesoscale droplet has advantages of easy for fabrication, natural materials, compact structure and low cost. Such a PHs may have applications in many fields, including temporal optics and optical switching, microscopy, sensors, materials processing, nonlinear optics, biomedicine, and so on.
Analytical model of a diode-pumped cesium laser for investigation of upper-state mixing and quenching reactions
Authors: Endo Masamori , Nagaoka Hiroki , Wani Fumio
Published: February 2023

A one-dimensional analytical model of a diode-pumped cesium vapor laser was constructed, and equations were provided to explain the dependence of the laser power on the hydrocarbon gas partial pressure. By varying the hydrocarbon gas partial pressure over a wide range and measuring the laser power, the corresponding mixing and quenching rate constants were determined. A gas-flow Cs diode-pumped alkali laser (DPAL) was operated with methane, ethane, and propane as buffer gases, varying the partial pressures from 0 to 2 atmospheres. The experimental results were in good agreement with the analytical solutions, confirming the validity of our proposed method. Separate 3-D numerical simulations were performed, and the output power effectively reproduced the experimental results over the entire buffer gas pressure range.
Structural similarities between the metacyclic and bloodstream form variant surface glycoproteins of the African trypanosome
Authors: Chandra Monica , Đaković Sara , Foti Konstantina , Zeelen Johan P. , van Straaten Monique , Aresta-Branco Francisco , Tihon Eliane , Lübbehusen Nicole , Ruppert Thomas , Glover Lucy , Papavasiliou F. Nina , Stebbins C. Erec
Published: February 2023

During infection of mammalian hosts, African trypanosomes thwart immunity using antigenic variation of the dense Variant Surface Glycoprotein (VSG) coat, accessing a large repertoire of several thousand genes and pseudogenes, and switching to antigenically distinct copies. The parasite is transferred to mammalian hosts by the tsetse fly. In the salivary glands of the fly, the pathogen adopts the metacyclic form and expresses a limited repertoire of VSG genes specific to that developmental stage. It has remained unknown whether the metacyclic VSGs possess distinct properties associated with this particular and discrete phase of the parasite life cycle. We present here three novel metacyclic form VSG N-terminal domain crystal structures (mVSG397, mVSG531, and mVSG1954) and show that they mirror closely in architecture, oligomerization, and surface diversity the known classes of bloodstream form VSGs. These data suggest that the mVSGs are unlikely to be a specialized subclass of VSG proteins, and thus could be poor candidates as the major components of prophylactic vaccines against trypanosomiasis.
PCR for detection of Leishmania donovani from microscopically negative tissue smears of suspected patients in Gondar, Ethiopia
Authors: Melkamu Roma , Berhane Nega , Jacobs Bart K. M. , Mohammed Rezika , Kassa Mekibib , Yeshanew Arega , Fikre Helina , Atnafu Saba , van Henten Saskia , van Griensven Johan , Pareyn Myrthe
Published: February 2023

Background

As untreated visceral leishmaniasis (VL) is fatal, reliable diagnostics are pivotal for accurate treatment allocation. The current diagnostic algorithm for VL in Ethiopia, which is based on the rK39 rapid diagnostic test and microscopy of tissue smears, lacks sensitivity. This probably leads to missed cases and patients not receiving treatment.

Methodology

We conducted a retrospective study on stored microscopically negative spleen and bone marrow smears from suspected VL patients collected at the Leishmaniasis Research and Treatment Center (LRTC) in Gondar, northern Ethiopia between June 2019 and November 2020. Sociodemographic, clinical and treatment data were collected and samples were tested by real-time PCR targeting kinetoplast DNA.

Principle findings

Among the 191 eligible samples (135 spleen and 56 bone marrow) with a microscopically negative and valid PCR result, 119 (62.3%) were positive by PCR, although Ct values for some were high (median 33.0). Approximately three quarters of these undiagnosed primary VL (77.3%) and relapse (69.6%) patients did not receive antileishmanial treatment. Of the 56 microscopically negative bone marrow samples, 46 (82.1%) were PCR positive, which is considerably higher compared to the microscopically negative spleen samples, for which 73 out of 135 (54.1%) were PCR positive. The odds of being PCR positive were significantly higher for bone marrow aspirates and higher when white blood cell values were lower and splenomegaly (in cm) was more pronounced.

Conclusions

This study demonstrates that a lot of suspected VL patients remain undiagnosed and untreated. This indicates the urgent need for better diagnostics for VL in the East-African region. The outcomes of PCR positive should be closely monitored and treatment should be provided if the patient deteriorates. In resource limited settings, implementation of PCR on bone marrow aspirate smears of patients with low WBC values and splenomegaly could lead to considerable improvements in patient management.
An investigation of the relation between life expectancy & socioeconomic variables using path analysis for Sustainable Development Goals (SDG) in Bangladesh
Authors: Nandi Dulal Chandra , Hossain Md. Farhad , Roy Pronoy , Ullah Mohammad Safi
Published: February 2023

In today’s world, the key variable for measuring population health is life expectancy (LE). The purpose of this research is to find out how life expectancy is related to other factors and develop a model to account for the predictors that contribute to LE. This study is also conducted to investigate and measure the effect of socioeconomic variables on LE in Bangladesh. In this study, the predictor variables are employment rate, gross national income (GNI), population growth rate, unemployment rate, and age dependency ratio. Path analysis disintegrated bivariate analysis and showed that employment rate, GNI, and age dependency ratio are significantly related to life expectancy, although bivariate analysis showed all variables are significantly related to LE. The maximum values of significant factors, GNI and employment rates, are $1930 and 21.32% happened in 2019, which is positively correlated with life expectancy. Also, the maximum value of the age dependency ratio (81.52%) happened in 1991, whereas the maximum value of the dependent variable LE (72.59 years) happened in 2019. It has been observed that LE, GNI, and employment rates all rise with one another. There exists an adverse relationship between LE and age dependency ratio. Based on comparisons with other highly developed nations, Bangladesh’s GNI needs to grow faster than other significant factors to boost life expectancy. We have forecasted variables that were significantly related to LE until 2030 for the purpose of sustainable development goals, especially the 3rd goal.
Long-term combined organic manure and chemical fertilizer application enhances aggregate-associated C and N storage in an agricultural Udalfs soil
Authors: Qiu Shaojun , Hu Cheng , Liu Donghai , Liu Shuanglai , Zhao Shicheng , Xu Xinpeng , Zhao Ying , He Ping , Zhou Wei
Published: February 2023

Little information is known on whether carbon (C) and nitrogen (N) immobilization is synchronized in different sizes of aggregates under different agricultural management practices. Carbon and N concentrations and the C/N ratios in different sizes of aggregates down to 40 cm depth were determined after long-term application of chemical fertilizers combined with manure or without manure in a wheat-rice cropping system. Manure application usually produced significantly (P < 0.05) higher C and N concentrations and lower C/N ratios in bulk soil and in different sizes of aggregates down to 20 cm depth than the other treatments, and the 1.5 MNPK treatment at 0–10 cm depth had the highest SOC concentration of 26.3 g/kg. The C and N concentrations in bulk soil and all aggregate fractions decreased markedly with increasing soil depth. Among water stable aggregates in all soil depths, the highest C (48.2–66.4%) and N (47.8–68.3%) concentrations as a percentage of SOC were found in the small macroaggregates (2000–250 μm, SM). Manure application significantly (P < 0.05) increased the mass and C and N concentrations of SM and SM fractions down to 20 depth. The mean C/N ratios of silt-clay within large and small macroaggregates (inter-SC) were 1.57 and 1.46 units lower than those of silt-clay particles, respectively, indicating that inter-SC had relative high N availability. Moreover, the C and N content of SM down to 40 cm depth tended to saturation with increasing C input rate. Overall, manure application effectively improved soil structure, SM were the dominant particles involved in soil C and N storage, and inter-SC were the main particles responsible for N availability.