bluuebunny/crossref_metadata_2025 huggingface dataset:
DUI Algorithm for improving the dynamic range of fiber optic distributed acoustic sensor
Authors: Fan Cunzheng , li Hao , liu Tao , Yan Zhijun , Liu Deming , Sun Qizhen
Published: February 2021

We proposed a differential-unwrapping-integral (DUI) algorithm for distortionless recovery of large amplitude acoustic signal in optical fiber DAS. The dynamic measurement range of phase demodulation could be increased by 82 times without sacrificing other performance.
Sinusoidal Silicon Waveguide Array for Optical Phased Array with Low Crosstalk
Authors: Yi Xiaogen , Zeng Huiying , Gao Sai , Qiu Ciyuan
Published: February 2021

We propose an ultra-compact low-crosstalk sinusoidal silicon waveguide array with a pitch of 695 nm, where the sinusoidal bends are keys to reduce the crosstalk between waveguides.
Toward fully integrated nonlinear photonics
Authors: Chang Lin , Xie Weiqiang , Bowers John E.
Published: February 2021

Two key advances recently made toward integrated nonlinear photonic circuits are presented, including an ultra-efficient (Aluminium) Gallium Arsenide on insulator nonlinear platform, and integrated turnkey soliton microcombs.
Soliton-molecule mode-locking via spectral filtering effect
Authors: Li Zilong , Guo Hairun , Liu Huanhuan
Published: February 2021

We demonstrate the generation of soliton molecules by means of the spectral filtering effect in mode-locked fiber lasers, and we implement the control on number of the bounded solitons by frequency tuning the filter component.
Optical phase-change materials (O-PCMs) for reconfigurable photonics
Authors: Zhang Yifei , Ríos Carlos , Shalaginov Mikhail Y. , An Sensong , Fowler Clayton , Chou Jeffrey B. , Roberts Christopher M. , Liberman Vladimir , Vitale Steven , Kang Myungkoo , Richardson Kathleen A. , Rivero-Baleine Clara , Gu Tian , Zhang Hualiang , Hu Juejun
Published: February 2021

O-PCMs uniquely offer exceptionally large refractive index modulation with minimal loss penalty, made possible through a dielectric-dielectric structural transition. Here we discuss our recent work on reconfigurable integrated photonics and metasurface based on O-PCMs.
Frequency Measurement Utilizing the Frequency Shift of Optical Frequency Combs
Authors: Ling Yuan , Liu Yong
Published: February 2021

A novel method of microwave frequency measurement is proposed and demonstrated by utilizing the frequency shift of optical frequency combs with a simplified system, enabling ultra-wide frequency measurement with its error less than 10kHz.
Massively-encoded optical data storage mediated by cylindrical vector beams and disordered nanoparticles
Authors: Xian Mingcong , Xu Yi , Ouyang Xu , Cao Yaoyu , Lan Sheng , Li Xiangping
Published: February 2021

We demonstrate that vectorial properties of cylindrical vector beams within the focal spot can boost the capacity of optical data storage in disordered nano-aggregates which shed new light on interaction between structured light and nanostructures.
27W world-record continuous power at room temperature from a 190μm-wide 808nm semiconductor broad-area laser
Authors: Huang Yifeng , Hu Martin H. , Ho James , Wang Weimin , Kuang Langxing , Qiu Yuzhen , Bai Xue , Liu Wenbin
Published: February 2021

We designed and fabricated an AlGaInAsP/AlGaAs quantum well laser diode working at wavelength of 808nm. At room temperature, a continuous wave thermal rollover power exceeding 27W was achieved from a 190μm wide LD.
Low-Complexity Nonlinear Equalizer for IM/DD Systems
Authors: Yu Yukui , Kim Hoon
Published: February 2021

We review our recently proposed nonlinear equalizer based on absolute operation for intensity-modulation/direct-detection systems. The proposed equalizer performs similar to the Volterra equalizer, but reduces the implementation complexity considerably.
Experimental Demonstration of Hierarchical Control over Multi-Vendor SDOTN Networks Based on Extended ACTN
Authors: Tan Yanxia , Zhang Yong , Zheng Yanlei , Liu Yacheng , Shi Yan , Zhou Yantao , Wang Guangquan , Ji Yuefeng
Published: February 2021

We demonstrate the provisioning of constrained connectivity services and protection functions using extended ACTN for multi-domain and multi-vendor software defined optical transport networks, which are validated in a multi-vendor testbed with commercial OTN equipment.
Reinforcement Learning-based Resource Allocation in Quantum Key Distribution Networks
Authors: Zuo Yingmin , Zhao Yongli , Yu Xiaosong , Nag Avishek , Zhang Jie
Published: February 2021

Efficient utilization of key resources is one of the key problems in quantum key distribution (QKD) networks. This paper verifies the effectiveness of using reinforcement learning to realize resource allocation in QKD networks.
NLFM Microwave Waveform Generation by Optically Injected Semiconductor Laser for Radar Applications
Authors: Zhang Renheng , Zhou Pei , Li Kunxi , Jiang Zhidong , Bao Hualong , Li Nianqiang
Published: February 2021

Photonic generation of nonlinear frequency-modulated (NLFM) microwave signals based on optically injected semiconductor laser has been demonstrated. Compared with LFM signals with the same bandwidth, a 13 dB improvement of peak-to-sidelobe ratio (PLSR) is found.
High-performance single-photon sources from solid-state quantum emitters
Authors: Wang Hui , Lu Chao-Yang , Pan Jian-Wei
Published: February 2021

We develop high-efficiency single- and entangled-photons sources that simultaneously combine high purity, efficiency, and indistinguishability. We develop elliptical microcavities to boost the polarized single-photon extraction efficiency over 50%. We coherently excite a quantum dot with a dichromatic pulsed laser to circumvent the 50% loss issue in resonance fluorescence due to the polarization-extinction configuration. We directly observe intensity squeezing of 0.59 dB in resonance fluorescence, and a corrected squeezing of 3.29 dB at the first lens. Quantum interference between quantum-dot single photons and sunlight is also demonstrated in our experiments.
Quantum Emitters in Two-dimensional Hexagonal Boron Nitride
Authors: Xu Zai-Quan , Li Chi , Mendelson Noah , Aharonovich Igor , Toth Milos
Published: February 2021

Quantum emitters (QEs) in hexagonal boron nitride (hBN) are critical components with potential applications in quantum technologies. This talk will review our recent study on fabrication, modulation of QEs in 2D hBN and integration to photonics resonators.
A Mixed-Signal Framework for Modelling Fourier-Domain Optical Coherence Tomography
Authors: Ling Yuye , Wang Mengyuan , Gan Yu , Yao Xinwen , Schmetterer Leopold , Zhou Chuanqing , Su Yikai
Published: February 2021

We investigate the signal digitization procedure in FD-OCT and propose a novel mixed-signal framework to model its image formation. It turns out FD-OCT is a shift-variant system, if conventional IDFT is used to reconstruct the images.
Performance Analysis of Transmitter One-Sample-per-Symbol Approach
Authors: Ke Jianhong , Tang Xuefeng , Li Chuandong
Published: February 2021

The performance of symbol-rate sampling transmitter with pre-emphasis is analyzed. The performance highly depends on the frequency response of the transmitter.
Experimental Demonstration of Hybrid FSO/RF System with Adaptive Link Selection and Switching
Authors: Song Song , Guo Lei , Xu Tianming , Yang Qianyuan , Liu Yejun
Published: February 2021

We propose and experimentally demonstrate a hybrid FSO/RF system with adaptive link selection and switching. FSO and RF links can be switched adaptively to different channel conditions for a robust transmission in changeable weather factor.
Network Resource Optimization with Latency Sensitivity in Collaborative Cloud-Edge Computing Networks
Authors: Liu Ling , Ma Weike , Chen Bowen , Gao Mingyi , Chen Hong , Wu Jinbing
Published: February 2021

This paper investigated the network resource optimization with latency sensitivity in collaborative cloud-edge computing networks. Simulation results show that the proposed approach optimize network resource allocation and reduce end-to-end (E2E) latency.
Photonic Random Bit Generation Based on Chaotic Laser Diodes for Wireless Distribution
Authors: Dong Jia-Xin , Ruan Jingya , Zhang Luan , Chan Sze-Chun
Published: February 2021

Random bits generated from physical entropy in the timing of microwave bursts are investigated using a laser diode. The bursts are generated by chaotic dynamics for yielding bits at gigabits per second for wireless distribution.
Optical Multipath RF Self-Interference Cancellation for Full-Duplex Communication
Authors: Su Xinxin , Fu Shuanglin , Wang Chao , Wu Zhenlin , Gu Yiying , Zhao Mingshan , Han Xiuyou
Published: February 2021

Optical multipath RF self-interference cancellation for full-duplex communication is proposed. The measured results show that the cancellation depth is 30dB over bandwidth 40 MHz at 6 GHz and the signal of interest is well recovered.
Monolithically Integrated Linear-Cascade Modified Uni-traveling-carrier Photodiodes
Authors: Chao Enfei , Xiong Bing , Han Yaru , Sun Changzheng , Hao Zhibiao , Wang Jian , Wang Lai , Han Yanjun , Li Hongtao , Yu Jiadong , Luo Yi
Published: February 2021

Linear-cascade modified uni-traveling-carrier photodiodes are monolithically integrated and exhibit a bandwidth improvement from 32 GHz to 54 GHz, which has been verified to result from the reduction of device capacitance due to the series structure.
Robust weighted principal components analysis demodulation algorithm for phase-shifting interferometry
Authors: Vargas Javier , Wang Shouyu , Gómez-Pedrero José A. , Estrada Julio C.
Published: February 2021

We present an asynchronous phase-shifting demodulation approach based on the principal component analysis demodulation method that is robust to typical problems as turbulence, vibrations, and temporal instabilities of the optical setup. The method brings together a two-step and a phase-shifting asynchronous demodulation method to share their benefits while reducing their intrinsic limitations. Thus, the proposed approach is based on a two-fold process. First, the modulating phase is estimated from a two-step demodulation approach. Second, this information is used to compute weights to each phase-shifted pattern of the interferogram sequence, which are used in a novel weighted principal component demodulation approach. The proposed technique has been tested with simulated and real interferograms affected by turbulence and vibrations providing very satisfactory results in challenging cases.
Polarization conversion metasurface design based on characteristic mode rotation and its application into wideband and miniature antennas with a low radar cross section
Authors: Shi Yan , Meng Hao Xuan , Wang Hua Jie
Published: February 2021

In this paper, a characteristic mode rotation (CMR) method has been proposed to design a compact metasurface antenna with a low radar cross section (RCS) in a wideband. In the proposed CMR method, the incident wave dependent complex characteristic currents corresponding to the dominant characteristic modes solved by the characteristic mode method (CMM) are calculated. With the direction of the superposition of the complex characteristic currents orthogonal to that of the incident electric field in the CMR method, the metasurface subarray with wideband polarization conversion characteristic is designed. By arranging the metasurface subarray in a rotation way, a metasurface array with a compact size of 1.28λ0×1.28λ0 is designed for wideband RCS reduction. A miniature circle patch antenna is integrated with the metasurface array to achieve not only good radiation performance but also low observability for the in-band and the out-of-band of the antenna. Simulated and measured results demonstrate that the proposed miniature metasurface antenna designed by the CMR method has a good broadside radiation pattern, a maximal gain of 10.75 dB, and a -10 dB RCS reduction characteristic in the wide band of 6∼20.7 GHz with a fractional band of 110%.
Adorym: a multi-platform generic X-ray image reconstruction framework based on automatic differentiation
Authors: Du Ming , Kandel Saugat , Deng Junjing , Huang Xiaojing , Demortiere Arnaud , Nguyen Tuan Tu , Tucoulou Remi , De Andrade Vincent , Jin Qiaoling , Jacobsen Chris
Published: February 2021

We describe and demonstrate an optimization-based X-ray image reconstruction framework called Adorym. Our framework provides a generic forward model, allowing one code framework to be used for a wide range of imaging methods ranging from near-field holography to fly-scan ptychographic tomography. By using automatic differentiation for optimization, Adorym has the flexibility to refine experimental parameters including probe positions, multiple hologram alignment, and object tilts. It is written with strong support for parallel processing, allowing large datasets to be processed on high-performance computing systems. We demonstrate its use on several experimental datasets to show improved image quality through parameter refinement.
Far UV-enhanced Al mirrors with a Ti seed film
Authors: Larruquert Juan I. , Honrado-Benítez Carlos , Gutiérrez-Luna Nuria , Ríos-Fernández Álvaro , López-Reyes Paloma
Published: February 2021

A Ti seed film is investigated towards improving the far UV reflectance of Al/MgF2 mirrors. Samples were initially coated with a Ti film in half of the area and they were later coated in the full area with an Al film and protected with MgF2. All materials were deposited by evaporation. Samples were prepared with the MgF2 layer deposited either at room temperature (RT) or at 225°C. A 3-nm thick Ti seed film was seen to significantly increase the reflectance of Al/MgF2 mirrors at the well-known reflectance dip centered at ∼160 nm; this was attributed to a reduction of short-range surface roughness at the Al/MgF2 interface, which is responsible for radiation absorption through surface-plasmon (SP) coupling. SP absorption was more efficiently reduced with a Ti seed film on samples fully deposited at RT. A Ti seed film as thin as 1 nm provided the largest SP absorption reduction, and the SP dip was almost completely removed.
Dynamically adjustable-induced THz circular dichroism and biosensing application of symmetric silicon-graphene-metal composite nanostructures
Authors: Wang Yongkai , Wang Qijing , Wang Qianying , Wang Yingying , Li Zhiduo , Lan Xiang , Dong Jun , Gao Wei , Han Qingyan , Zhang Zhongyue
Published: February 2021

Induced circular dichroism (ICD) has been used to detect biomolecular conformations through the coupling between chiral molecules and achiral metal nanostructures with the localized surface plasmon (LSP). However, this ICD is always weak and cannot be dynamically adjusted. Here, we put dielectric and graphene nanostructures on a metal-substrate for restricting more light energies and obtaining dynamic adjustable performance. A composite nanostructure array composed of achiral silicon-nanorods on a metal-substrate and graphene-ribbons (ASMG) is theoretically investigated. Two strong ICD signals appear in the THz region. Near-field magnetic distributions of ASMG reveal that the two strong ICD signals are mainly due to the surface plasmon resonances (SPPs) on the metal-substrate and LSP in the graphene nanostructures, respectively. The ICD signals strongly depend on the geometric parameters of ASMG and are dynamically adjusted by just changing the Fermi levels of graphene-ribbons. In addition, left-handed ASMG and right-handed ASMG can be used to identify the chiral molecular solutions with different chiralities. The maximum enhancement factor of the chiral molecular solutions could reach up to 3500 times in the THz region. These results can help to design dynamically adjustable THz chiral sensors and promote their application in biological monitoring and asymmetric catalysis.
Mid-infrared nonlinear optical performances of Ge-Sb-S chalcogenide glasses
Authors: Hu Yongsheng , Tian Kangzhen , Li Tongtong , Zhang Mingjie , Ren He , Qi Sisheng , Yang Anping , Feng Xian , Yang Zhiyong
Published: February 2021

We report a systematical investigation on the mid-infrared nonlinear performances of Ge-Sb-S glasses. Laser damage threshold (Ith) of Ge-Sb-S glasses was measured under femtosecond pulsed laser incidence ranging between 1.55-3.6 μm. It is found that the Ith has the maximum value at stoichiometric composition. Moreover, the relationship between the refractive index refractive (n0) and nonlinear refractive indices (n2) was obtained, following the semi-empirical Miller’s rule. The n2 shows a nonlinear decay with the increase of wavelength. The multi-photon (up to 7-photon) absorption coefficients of Ge-Sb-S glasses were characterized. The composition Ge25Sb10S65 with high Ith was selected as the core of the designed fiber. A compatible composition Ge25Sb8S67 was chosen as the cladding glass. A 10 μm-diameter-core fiber was made via rod-in-tube method. By pumping a 10-cm-long fiber at 4.8 μm with 170 fs (100 kHz) pulses, we achieved a supercontinuum covering the 3–8 μm spectral range. It indicates that Ge-Sb-S glass family is a type of environment-friendly host materials for mid-infrared nonlinear applications.
Electronic Multidimensional Spectroscopy Reveals the Functional Charge Transfer State in Bacterial Reaction Centers
Authors: Bukartė E. , Paleček D. , Edlund P. , Westenhoff S. , Zigmantas D.
Published: February 2021

The high efficiency of the special pair in initiating electron transfer in reaction centers is not well understood. By using 2DES, we identified the charge transfer state, which is responsible for the charge separation function.
Ultrafast charge and energy transfer in a MoSe2/WSe2 heterostructure
Authors: Cundiff Steven T. , Purz Torben L. , Martin Eric W. , Rivera Pasqual , Xu Xiaodong
Published: February 2021

We examine ultrafast charge and energy transfer in a MoSe2/WSe2 heterostruc-ture using multi-dimensional coherent spectroscopy. This technique identifies transfer processes and indicates charge and energy transfer times below 200 fs and 900 fs, respectively.
Photoinduced Intersubband Absorption and Enhanced Photobleaching in Twisted Bilayer Graphene
Authors: Pogna Eva A. A. , Miao Xianchong , von Dreifus Driele , Alencar Thonimar V. , Moutinho Marcus V. O. , Venezuela Pedro , Chiu Po-Wen , Manzoni Cristian , Cerullo Giulio , Ji Minbiao , de Paula Ana M.
Published: February 2021

High-sensitivity femtosecond microscopy with broad spectral coverage reveals photoinduced intersubband absorption and enhanced photobleaching bands in twisted bilayer graphene endowed with picosecond relaxation time and twist angle-tunable energy position.
Determination of mode-projected electron-phonon coupling from time-domain observations of microscopic scattering processes
Authors: Na M. , Mills A. K. , Boschini F. , Michiardi M. , Nosarzewski B. , Day R. P. , Razzoli E. , Sheyerman A. , Schneider M. , Levy G. , Zhdanovich S. , Devereaux T. P. , Kemper A. F. , Jones D. J. , Damascelli A.
Published: February 2021

Using a femtosecond extreme ultraviolet source with a narrow linewidth, we observe electrons in graphite scattering with the

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phonon from optically-populated initial states to well-defined final states, and extract the electron-phonon matrix element.
Laser induced periodic surface structures on Yttria-stabilized Zirconia ceramics formed by time-dependent polarization pulses
Authors: Kakehata M. , Yashiro H.
Published: February 2021

Time-dependent polarization pulses generated by combinations of two pulses (orthogonal polarized or counter-rotating circularly polarized) were irradiated on yttria-stabilized zirconia ceramics and formed laser-induced periodic surface structures. Formed structures show effects of evolution of the polarization state and intensity.
Ultrafast Dynamics in Ge2Sb2Te5 Thin Films during Laser-Induced Successive Surface Modification
Authors: Kobayashi M. , Arashida Y. , Asakawa K. , Konishi K. , Yumoto J. , Kuwata-Gonokami M. , Takeda J. , Katayama I.
Published: February 2021

Laser-induced multi-timescale surface modification of Ge2Sb2Te5 thin films was investigated using high-repetition-rate single-shot pump-probe spectroscopy. The successive measurement of ultrafast dynamics during formation of laser-induced periodic surface structure reveals pulse-to-pulse reduction of the relaxation time. ©2020 The Authors
Ultrafast generation of coherent acoustic phonons with THz picoseconds pulses in metals and topological insulators nanofilms
Authors: Levchuk A. , Vaudel G. , Wilk B. , Labbé F. , Arnaud B. , Balin K. , Szade J. , Ruello P. , Juvé V.
Published: February 2021

We report for the first time the generation of coherent acoustic phonons in materials with terahertz ultrashort pulses. This is demonstrated in metals and topological insulators by exciting acoustic eigenmode in nanometric sized thin films.
Effect of Laser Pulse Fluence, Waveform and Film Thickness on Ultrafast Magnetization Dynamics in Nickel
Authors: Zanjani Saeedeh Mokarian , Onbaşlı Mehmet Cengiz
Published: February 2021

The effect of femtosecond laser pulse parameters on ultrafast magnetization dynamics in Nickel films is modeled. For Gaussian laser pulse (unlike sinc), Ni recovers its magnetization in one picosecond within an optimal laser fluence range.
Ultrafast probing of soot dynamics using near-infrared filament pump and UV laser probe
Authors: Zang Hongwei , Fu Yao , Hou Mengyao , Li Helong , Yamanouchi Kaoru , Xu Huailiang
Published: February 2021

We propose a near-infrared filament pump and an ultraviolet light probe approach to measure the dynamics of soot in flames with femtosecond time resolution, and demonstrate unexpected ultrafast swelling and shrinking processes of soot nanoparticles.
Tracking Ultrafast Charge Separation in a PBI-based Biomimetic Complex for Oxygen Evolution
Authors: Maiuri Margherita , Russo Mattia , Moretti Luca , Petropoulos Vasilis , Rigodanza Francesco , Sartorel Andrea , Prato Maurizio , Cerullo Giulio , Bonchio Marcella
Published: February 2021

Multidimensional spectroscopies reveal a two-step process in a biomimetic supracomplex for oxygen evolution. A sub-ps charge-separation within the light-sensitizer moiety is followed by hole transfer from the catalyst counterpart, forming productive charges.
Ultrafast Z→E and E→Z Photoswitching Dynamics of Oxadiazocine Unveiled by Femtosecond Transient Electronic Absorption Spectroscopy
Authors: Bank Dennis , Renth Falk , Hammerich Melanie , Lentes Pascal , Herges Rainer , Temps Friedrich
Published: February 2021

We investigated the Z→E and E→Z photoswitching dynamics of oxadiazocine by fs electronic absorption spectroscopy supported by ab initio calculations. The Etwist isomer is formed via an Echair intermediate in ~15 ps, the Zboat isomer results from Etwist via a direct route in ~230 fs.
Direct Observation and Kinetic Mapping of Point-to-Point Proton Transfer to Multiple Competing Molecular Sites
Authors: Pines Ehud , Pines Dina , Huppert Dan
Published: February 2021

The complex ps-resolved fluorescence-decay profiles of a photoacid undergoing reversible geminate-recombination reaction is used to kinetically analyze point-to-point proton transfer to three competing molecular recombination sites which are identified by their characteristic proton retention times.
Two-dimensional electronic spectroscopy reveals distinct ultrafast photophysics in tricarbocyanine dyes: Polar solvation and photo-isomerization
Authors: Silori Yogita , Seliya Pankaj , De Arijit K.
Published: February 2021

Using two-dimensional electronic spectroscopy, here we show how near-infrared tricarbocyanine dyes, DNTTCI and IR140, exhibit distinct excited-state relaxation pathways on ultrafast time-scale, polar solvation and photo-isomerization, respectively, which further depends on excitation wavelength.
The ultrafast excited state relaxation dynamics of nano-assemblies of Chlorophyll a
Authors: Silori Yogita , Chawla Sakshi , De Arijit K.
Published: February 2021

Using femtosecond pump-probe spectroscopy, we explore the ultrafast excited state relaxation dynamics of two types of supramolecular assemblies (rod-shaped and spherical micelles) of chlorophyll-a, formed at different ratios of ACN/water.
Femtosecond Molecular Flattening in [Cu(dmp)2]+ Probed by X-ray Emission Spectroscopy and Solution Scattering
Authors: Choi Tae-Kyu , Khakhulin Dmitry , Vankó György , Németh Zoltán , Szlachetko Jakub , Yabashi Makina , Penfold Thomas J. , Gawelda Wojciech , Katayama Tetsuo
Published: February 2021

Femtosecond electronic and nuclear dynamics in [Cu(dmp)2]+ complex upon 550 nm photoexcitation are studied with X-ray emission spectroscopy and X-ray solution scattering, revealing pseudo Jahn-Teller distortion (~410 fs) coupled with coherent vibrational motion.
Charge generation mediated by bound polaron pairs and delocalized charge transfer states in non-fullerene organic solar cells
Authors: Song Yin , Liu Xiao , Li Yongxi , Nguyen Hoang Huy , Duan Rong , Kubarych Kevin J. , Forrest Stephen R. , Ogilvie Jennifer P.
Published: February 2021

Using two-dimensional electronic and electronic-vibrational spectroscopies, we find that charge generation via both electron and hole transfer pathways are mediated by bound polaron pairs and delocalized charge-transfer states in non-fullerene organic photovoltaics.
Symmetry of Molecular Rydberg States Revealed by XUV Transient Absorption Spectroscopy
Authors: Peng Peng , Marceau Claude , Hervé Marius , Corkum P. B. , Naumov A. Yu. , Villeneuve D. M.
Published: February 2021

We studied Rydberg states of N2 and O2 by XUV transient absorption spectroscopy. We were able to determine the polarization direction of the electronic transitions, and hence identify the symmetry of the final states.
CEP Current Control in Dielectrics and Wide-Bandgap Semiconductors with nJ-Class Laser Pulses
Authors: Hanus Václav , Csajbók Viktória , Pápa Zsuzsanna , Budai Judit , Sándor Péter , Molnár György , Volk János , Dombi Péter
Published: February 2021

We report on the detection of optically induced lightwave-driven currents in GaN and SiO2 achieved with laser oscillator pulses (80 MHz repetition rate) for the first time to our knowledge. We demonstrate sensitivity of the current direction on the carrier-envelope phase (CEP) of the pulses.
Dielectric laser accelerators: attosecond electron bunch creation and complex phase-space control
Authors: Schönenberger Norbert , Mittelbach Anna , Yousefi Peyman , McNeur Joshua , Niedermayer Uwe , Li Ang , Hommelhoff Peter
Published: February 2021

We show that dielectric laser accelerators (DLA), photonic nano-structures illuminated by ultrashort laser pulses, can generate attosecond electron bunch trains of 280 as length and allow other complex phase-space manipulation.
Tracking Structural Dynamics during Charge Separation Processes with Time-Resolved Impulsive Stimulated Raman Spectroscopy
Authors: Kim Dongho
Published: February 2021

Structural dynamics during charge separation in donor-acceptor-type molecules were investigated by time-resolved impulsive stimulated Raman spectroscopy. Our results stress the time-domain Raman technique is a powerful method to observe structural changes in light-induced charge-separation reaction.
Dynamic electron energy and momentum mapping for ultrafast intervalley relaxation in layered WSe2
Authors: Yamaguchi Hiroya , Kato Keiko , Mashiko Hiroki , Sekine Yoshiaki , Hibino Hiroki , Katayama Ikufumi , Takeda Jun , Oguri Katsuya
Published: February 2021

Dynamical energy and momentum mapping for intervalley electron transfer in WSe2 was investigated with high-harmonic-based ultrafast ARPES. The measured ultrashort scattering time of 30 fs will provide a guide to lightwave control of valley pseudospin.
High-sensitivity time-resolved reflectivity in extreme ultraviolet region for probing carrier and phonon dynamics
Authors: Kato Keiko , Mashiko Hiroki , Kunihashi Yoji , Omi Hiroo , Gotoh Hideki , Oguri Katsuya
Published: February 2021

A highly sensitive method for measuring time-resolved reflection in extreme ultraviolet region was developed. We observed optical modulation ΔR/R~1×10-4 by boxcar integration and lock-in detection, and the data acquisition takes four minutes.
Single-Shot Transient Absorption of Nascent Perovskite Nanocrystals
Authors: Sadighian James C. , Wilson Kelly S. , Crawford Michael L. , Wong Cathy Y.
Published: February 2021

Perovskite nanocrystals are measured with single-shot transient absorption during synthesis. The lineshape indicates that carriers in nascent nanocrystals become trapped at the surface, inducing internal electric fields. The evolving lineshape reports surface passivation during synthesis.
Blueshift of the TO Phonon Resonance in GaAs by Femtosecond Electron-Hole Excitation
Authors: Reimann K. , Ghalgaoui A. , Woerner M. , Elsaesser T. , Flytzanis C. , Biermann K.
Published: February 2021

After electron-hole generation by femtosecond near-infrared pulses, the TO-phonon resonance in GaAs is blueshifted by 100 GHz as observed via a fourth-order non-linear THz emission.
Coherent electron-phonon couplings in a charge density wave material
Authors: Zhang Yingchao , Shi Xun , You Wenjing , Tao Zhensheng , Zhong Yigui , Kabeer Fairoja Cheenicode , Maldonado Pablo , Oppeneer Peter M. , Bauer Michael , Rossnagel Kai , Kapteyn Henry , Murnane Margaret
Published: February 2021

Using trARPES, we observe that the CDW amplitude mode in 1T-TaSe2 can coherently modulate the electron temperature. Coherent electron-phonon coupling mechanisms are proposed to explain the electron temperature oscillations at different pump fluences.
Organic quantum batteries
Authors: Quach J. Q. , Virgili T. , Cerullo G. , McGhee K. E. , Ganzer L. , Lidzey D. G.
Published: February 2021

By ultrafast spectroscopy we provide experimental evidence of superextensive charging in organic quantum batteries constructed as microcavities based on a double dielectric-mirror structure containing a thin film of a Lumogen-F dye blended in a polystyrene matrix.
Large-Scale Ab Initio Calculation of Ultrafast Dynamics in Thin-Film Dielectrics
Authors: Yabana Kazuhiro , Hirokawa Yuta , Yamada Atsushi , Yamada Shunsuke , Noda Masashi , Uemoto Mitsuharu , Boku Taisuke
Published: February 2021

We have achieved a large-scale ab initio simulation of light-matter interaction over 10,000 atoms. Nonlinear optical phenomena in glass thin film including high harmonic generation and light-matter energy transfer are described with unprecedented details.
Angle-resolved Photoelectron Spectroscopy of large Water Clusters ionized by an XUV Comb
Authors: Colaizzi Lorenzo , Ban Loren , Wanie Vincent , Saraswathula Krishna , Månsson Erik P. , Rupp Philipp , Liu Qingcao , Seiffert Lennart , Herzig Elisabeth A. , Cartella Andrea , Yoder Bruce L. , Trabattoni Andrea , Kling Matthias , Fennel Thomas , Signorell Ruth , Calegari Francesca
Published: February 2021

We performed angle-resolved photoelectron spectroscopy of water clusters ionized by an extreme-ultraviolet attosecond pulse train. A clean signature of the clusters was isolated from the water monomer contribution, to be used for time-resolved attosecond spectroscopy.
Symmetry aspects of attosecond transient absorption spectroscopy in a dielectric crystal
Authors: Yamada Shunsuke , Yabana Kazuhiro
Published: February 2021

A relation between the crystalline symmetry and the transient modulation of optical properties of dielectric crystal in attosecond transient absorption spectroscopy is presented. Taking 4H-SiC as an example, first-principles calculations confirm the symmetry relation.
Coherently and Fluorescence-Detected Four- and Six-Wave-Mixing Two-Dimensional Electronic Spectroscopy: Measuring Multi-Exciton Dynamics and Delocalization
Authors: Malý Pavel , Müller Stefan , Lüttig Julian , Schreck Maximilian , Lambert Christoph , Brixner Tobias
Published: February 2021

We directly compare nonlinear coherently and fluorescence-detected two-dimensional electronic spectra of electronically coupled squaraine heterodimers. By identifying signatures of multi-exciton nonequilibrium dynamics and delocalization, we establish grounds for interpretation of these nonlinear spectroscopy implementations.
Laser-Enabled Control of Interatomic-Coulomb-Decay Dynamics
Authors: Hogle Craig W. , Martin Leigh , Tong Xiao-Min , Ueda Kiyoshi , Miteva Tsveta , Cederbaum Lorenz S. , Kapteyn Henry C. , Murnane Margaret M. , Ranitovic Predrag
Published: February 2021

Interatomic-Coulombic-Decay (ICD) processes play an important role in the interaction of X-rays with biological systems. Here, we present the first successful experimental demonstration that enables and precisely times the outcome of an ICD process in an argon dimer, utilizing ultrafast XUV and IR radiation.
Tunable Third Harmonic Vacuum Ultraviolet Coherent Light Generation Using Dielectric Nanomembranes
Authors: Konishi K. , Akai D. , Mita Y. , Ishida M. , Yumoto J. , Kuwata-Gonokami M.
Published: February 2021

We demonstrate a simple and practical method for generating tunable coherent vacuum ultraviolet light with an adequate intensity for spectroscopic application such as ARPES based on third harmonic generation in dielectric free-standing nanomembranes.
Stabilization of Mach Zehnder Interferometer in a sub-cycle shortwave-infrared OPA system
Authors: Lin Yu-Chieh , Nabekawa Yasuo , Midorikawa Katsumi
Published: February 2021

We demonstrate a technique to stabilize a Mach Zehnder Interferometer (MZI) including an AOPDF in each interferometer arm, which is utilized for compensating for the dispersion of an over-octave shortwave-infrared spectrum ranging from 0.9 to 2.4 µm. The relative phase jitter was estimated to be 130 mrad. This scheme was adopted in the OPA system generating 4.4 fs (0.73 cycles) pulses at 1.8 µm.
Post-Compression of Picosecond Pulses to Four Optical Cycles via Multi-Pass Spectral Broadening
Authors: Balla Prannay , Wahid Ammar Bin , Sytcevich Ivan , Guo Chen , Viotti Anne-Lise , Silletti Laura , Cartella Andrea , Alisauskas Skirmantas , Tavakol Hamed , Grosse-Wortmann Uwe , Schönberg Arthur , Seidel Marcus , Manschwetus Bastian , Lang Tino , Trabattoni Andrea , Calegari Francesca , Couairon Arnaud , L’Huillier Anne , Arnold Cord L. , Hartl Ingmar , Heyl Christoph M.
Published: February 2021

We demonstrate post-compression of 1.2 ps pulses to the few-cycle regime via multi-pass spectral broadening. We achieve compression factors of 40 via single and >90 via dual stage compression employing mJ pulses.
Elliptical terahertz generation by two-color lineally polarized strong laser pulses
Authors: Wang Guo-Li , Zhang Wen-Tao , Zhang Lei
Published: February 2021

We theoretically investigate the polarization characteristics of terahertz radiations generated by two-color nonparallel linearly polarized ω and 2ω pulses. Some new findings are worthy of confirmation with more investigations.
Probing spectral and temporal fine structures of high-order harmonic generation in laser-driven electron-rescattering
Authors: Han Lin , Jiao Zhi-Hong , Li Peng-Cheng , Chu Shih-I
Published: February 2021

We present an ab initio precision investigation of the subtle details of the spectral and temporal fine structures of high-order harmonic generation (HHG) in laser-driven electron-rescattering by using a new synchrosqueezing transform method (SST). The SST time-frequency analysis allows us to explore the in depth dynamics and contributions of the quantum trajectories in HHG associated with the electron-rescattering. Particularly it uncovers the subtle details of the spectral and temporal fine structures of the HHG and provides novel insights regarding the dynamical origin of the HHG in below-threshold harmonic regimes.
Gauge-Invariant Time-Dependent Configuration Interaction Singles Method for Molecular Strong Field Physics
Authors: Teramura Takuma , Sato Takeshi , Ishikawa Kenichi L.
Published: February 2021

We present a numerical implementation of the gauge-invariant time-dependent configuration interaction singles method for high-order harmonic generation in molecules. We demonstrate successful simulations for propane of low symmetry.
Supercontinuum spectral phase interferometry with isolated attosecond pulse
Authors: Mashiko Hiroki , Oshima Akihiro , Chen Ming-Chang , Asaga Koji , Katayama Ikufumi , Takeda Jun , Nishikawa Tadashi , Oguri Katsuya
Published: February 2021

We demonstrate supercontinuum spectral phase interferometry with an isolated attosecond pulse (IAP). The interferogram indicates a high degree of temporal coherence over the full IAP continuous spectrum, which will contribute to exploring dispersive electron dynamics. 1. Introduction Combining spatial and temporal detection by means of self-referencing interferometry with high-order harmonics has a variety of applications in, for instance, molecular orbital tomography [1], nanoscale sample imaging [2], and the characterization of complex electron dynamics [3]. Meanwhile, an isolated attosecond pulse (IAP) with short duration and broadband supercontinuum spectrum have contributed to observing ultrafast electronic motions in various targets [4]. The self-referencing interferometry with two IAPs will be an important tool for observing electron dynamics through the phase-based spectroscopy. Here, we demonstrated the supercontinuum spectral phase interferometry with IAP [5]. The coherence over broadband spectral region will contribute to studying the dispersive electron dynamics through Fourier spectroscopy.
Ultrafast Thin-Disk based CPA System with >.1kW Output Power and <.500 fs Pulse Duration
Authors: Wandt Christoph , Herkommer Clemens , Jung Robert , Klingebiel Sandro , Krötz Peter , Rampp Michael , Teisset Catherine Y. , Michel Knut , Metzger Thomas
Published: February 2021

A thin-disk based CPA system with a maximum compressed pulse energy of 260 mJ at a repetition rate of 1 kHz and output powers close to 2 kW at 20 kHz is presented. Spectral amplitude shaping led to pulse durations of < 500 fs at 206 mJ.
Vectorial Shaping of Ultrafast Pulses using Dielectric Metasurfaces
Authors: Chen Lu , Zhu Wenqi , Song Junyeob , Huo Pengcheng , Strait Jared , Zhang Cheng , Lezec Henri J. , Xu Ting , Agrawal Amit
Published: February 2021

We demonstrate a dielectric-metasurface-enabled pulse shaper able to tailor the temporal polarization of near-infrared femtosecond pulses over an ultrawide bandwidth, allowing three-dimensional vector-shaped pulses exhibiting rich time-evolving instantaneous polarization states within a single pulse.
Femtosecond nano-imaging of the few-femtosecond coherent dynamics of two-dimensional materials
Authors: Jiang Tao , Luo Wenjin , Kravtsov Vasily , Tokman Mikhail , Belyanin Alexey , Raschke Markus B.
Published: February 2021

Using plasmonic nanofocusing coupled with ultrafast femtosecond pulses, we perform spatio-temporal nonlinear optical imaging of graphene and MoSe2. We resolve for the first time the nanoscale heterogeneity in the few-femtosecond coherent dynamics in two-dimensional materials.
Controlled Optical Waveforms for Extremely Efficient Chiral Discrimination on Ultrafast Time Scales
Authors: Ayuso David , Ordonez Andres , Ivanov Misha , Smirnova Olga
Published: February 2021

We demonstrate the ultimate efficiency in chiral discrimination using focused pulses of linearly polarized light. Sub-cycle control of the incident light wave enables full control over the enantio-sensitive response of chiral matter, exposing molecule-specific fingerprints.
Progress towards onchocerciasis elimination in Côte d’Ivoire: A geospatial modelling study
Authors: Eneanya Obiora A. , Koudou Benjamin G. , Aboulaye Meite , Elvis Aba Ange , Souleymane Yeo , Kouakou Marie-Madeleine , Weil Gary J. , Fischer Peter U.
Published: February 2021

Background

Côte d’Ivoire has had 45 years of intervention for onchocerciasis by vector control (from 1975 to 1991), ivermectin mass drug administration (MDA) (from 1992 to 1994) and community directed treatment with ivermectin (CDTi) from 1995 to the present. We modeled onchocerciasis endemicity during two time periods that correspond to the scale up of vector control and ivermectin distribution, respectively. This analysis illustrates progress towards elimination during these periods, and it has identified potential hotspots areas that are at risk for ongoing transmission.

Methods and findings

The analysis used Ministry of Health skin snip microfilaria (MF) prevalence and intensity data collected between 1975 and 2016. Socio-demographic and environmental factors were incorporated into a predictive, machine learning algorithm to create continuous maps of onchocerciasis endemicity. Overall predicted mean MF prevalence decreased from 51.8% circa 1991 to 3.9% circa 2016. The model predicted infection foci with higher prevalence in the southern region of the country. Predicted mean community MF load (CMFL) decreased from 10.1MF/snip circa 1991 to 0.1MF/snip circa 2016. Again, the model predicts foci with higher Mf densities in the southern region. For assessing model performance, the root mean squared error and R2 values were 1.14 and 0.62 respectively for a model trained with data collected prior to 1991, and 1.28 and 0.57 for the model trained with infection survey data collected later, after the introduction of ivermectin. Finally, our models show that proximity to permanent inland bodies of water and altitude were the most informative variables that correlated with onchocerciasis endemicity.

Conclusion/Significance

This study further documents the significant reduction of onchocerciasis infection following widespread use of ivermectin for onchocerciasis control in Côte d’Ivoire. Maps produced predict areas at risk for ongoing infection and transmission. Onchocerciasis might be eliminated in Côte d’Ivoire in the future with a combination of sustained CDTi with high coverage, active surveillance, and close monitoring for persistent infection in previously hyper-endemic areas.
What do blind people “see” with retinal prostheses? Observations and qualitative reports of epiretinal implant users
Authors: Erickson-Davis Cordelia , Korzybska Helma
Published: February 2021

Introduction

Retinal implants have now been approved and commercially available for certain clinical populations for over 5 years, with hundreds of individuals implanted, scores of them closely followed in research trials. Despite these numbers, however, few data are available that would help us answer basic questions regarding the nature and outcomes of artificial vision: what do recipients see when the device is turned on for the first time, and how does that change over time?

Methods

Semi-structured interviews and observations were undertaken at two sites in France and the UK with 16 recipients who had received either the Argus II or IRIS II devices. Data were collected at various time points in the process that implant recipients went through in receiving and learning to use the device, including initial evaluation, implantation, initial activation and systems fitting, re-education and finally post-education. These data were supplemented with data from interviews conducted with vision rehabilitation specialists at the clinical sites and clinical researchers at the device manufacturers (Second Sight and Pixium Vision). Observational and interview data were transcribed, coded and analyzed using an approach guided by Interpretative Phenomenological Analysis (IPA).

Results

Implant recipients described the perceptual experience produced by their epiretinal implants as fundamentally, qualitatively different than natural vision. All used terms that invoked electrical stimuli to describe the appearance of their percepts, yet the characteristics used to describe the percepts varied significantly between recipients. Artificial vision for these recipients was a highly specific, learned skill-set that combined particular bodily techniques, associative learning and deductive reasoning in order to build a “lexicon of flashes”—a distinct perceptual vocabulary that they then used to decompose, recompose and interpret their surroundings. The percept did not transform over time; rather, the recipient became better at interpreting the signals they received, using cognitive techniques. The process of using the device never ceased to be cognitively fatiguing, and did not come without risk or cost to the recipient. In exchange, recipients received hope and purpose through participation, as well as a new kind of sensory signal that may not have afforded practical or functional use in daily life but, for some, provided a kind of “contemplative perception” that recipients tailored to individualized activities.

Conclusion

Attending to the qualitative reports of implant recipients regarding the experience of artificial vision provides valuable information not captured by extant clinical outcome measures.
Evaluation of COVID-19 related knowledge and preparedness in health professionals at selected health facilities in a resource-limited setting in Addis Ababa, Ethiopia
Authors: Desalegn Zelalem , Deyessa Negussie , Teka Brhanu , Shiferaw Welelta , Yohannes Meron , Hailemariam Damen , Addissie Adamu , Abagero Abdulnasir , Kaba Mirgissa , Abebe Workeabeba , Abrha Alem , Nega Berhanu , Ayele Wondimu , Haile Tewodros , Gebrehiwot Yirgu , Amogne Wondwossen , Kantelhardt Eva Johanna , Abebe Tamrat
Published: February 2021

Background

The World Health Organization has declared that infection with SARS-CoV-2 is a pandemic. Experiences with SARS in 2003 and SARS-CoV-2 have shown that health professionals are at higher risk of contracting COVID-19. Hence, it has been recommended that aperiodic wide-scale assessment of the knowledge and preparedness of health professionals regarding the current COVID-19 pandemic is critical.

Objectives

This study aimed to assess the knowledge and preparedness of health professionals regarding COVID-19 among selected hospitals in Addis Ababa, Ethiopia.

Methods

A facility-based cross-sectional study was conducted from the last week of March to early April, 2020. Government (n = 6) and private hospitals (n = 4) were included. The front-line participants with high exposure were proportionally recruited from their departments. The collected data from a self-administered questionnaire were entered using EpiData and analyzed in SPSS software. Both descriptive statistics and inferential statistics (chi-square tests) are presented.

Results

A total of 1334 health professionals participated in the study. The majority (675, 50.7%) of the participants were female. Of the total, 532 (39.9%) subjects were nurses/midwives, followed by doctors (397, 29.8%) and pharmacists (193, 14.5%). Of these, one-third had received formal training on COVID-19. The mean knowledge score of participants was 16.45 (±4.4). Regarding knowledge about COVID-19, 783 (58.7%), 354 (26.5%), and 196 (14.7%) participants had moderate, good, and poor knowledge, respectively. Lower scores were seen in younger age groups, females, and non-physicians. Two-thirds (63.2%) of the subjects responded that they had been updated by their hospital on COVID-19. Of the total, 1020 (76.5%) participants responded that television, radio, and newspapers were their primary sources of information. Established hospital preparedness measures were confirmed by 43–57% of participants.

Conclusion

The current study revealed that health professionals in Addis Ababa, Ethiopia, already know important facts but had moderate overall knowledge about the COVID-19 pandemic. There were unmet needs in younger age groups, non-physicians, and females. Half of the respondents mentioning inadequate preparedness of their hospitals point to the need for more global solidarity, especially concerning the shortage of consumables and lack of equipment.