2023

• Record 49 of
  
  Title:Compact remote Raman system and its applications under strong sunlight research
  
  Author(s):Li, Zhicong(1,2); Xue, Bin(1); Zhao, Yiyi(1); Huang, Shuaidong(1,2); Liu, Yiheng(3); Ling, Zongcheng(3); Yang, Jianfeng(1)
  Source: OSA Continuum  Volume: 2  Issue: 8  Article Number: null  DOI: 10.1364/OPTCON.489969  Published: August 15, 2023  
  Abstract:Raman signal with a high signal-to-noise ratio (SNR) under a strong sunlight environment of 30000∼60000 Lux is very hard to obtain. A compact remote Raman spectrometer (CRS) has been developed for the purpose of detecting diverse types of lunar and earth minerals. The system comprises a spectrometer that is equipped with an ICCD detector, a 30 mm entry pupil diameter beam expander, and a 532 nm Nd: YAG Q-switched laser serving as the source of Raman scattering. The implementation of synchronous trigger and gating technology effectively overcomes the impact of strong sunlight. We obtained Raman spectra using a shorter integration time than in previous studies. The experimental results demonstrate that the detection of remote Raman spectroscopy under intense sunlight conditions facilitates the identification of silicates that have been discovered on the moon. © 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
  Accession Number: 20233714728632
• Record 50 of
  
  Title:On-chip Ce:YIG/Si Mach–Zehnder optical isolator with low power consumption
  
  Author(s):Liang, Jiachang(1); Li, Yan(1); Dai, Tingge(2); Zhang, Yuejun(1); Zhang, Xiaowei(1); Liu, Hongjun(3); Wang, Pengjun(4)
  Source: Optics Express  Volume: 31  Issue: 5  Article Number: null  DOI: 10.1364/OE.482805  Published: February 27, 2023  
  Abstract:The integrated optical isolator is an essential building block in photonic integrated chips. However, the performance of on-chip isolators based on the magneto-optic (MO) effect has been limited due to the magnetization requirement of permanent magnets or metal microstrips on MO materials. Here, an MZI optical isolator built on a silicon-on-insulator (SOI) without any external magnetic field is proposed. A multi-loop graphene microstrip operating as an integrated electromagnet above the waveguide, instead of the traditional metal microstrip, generates the saturated magnetic fields required for the nonreciprocal effect. Subsequently, the optical transmission can be tuned by varying the intensity of currents applied on the graphene microstrip. Compared with gold microstrip, the power consumption is reduced by 70.8%, and temperature fluctuation is reduced by 69.5% while preserving the isolation ratio of 29.44 dB and the insertion loss of 2.99 dB at1550 nm. © 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
  Accession Number: 20231013662315
• Record 51 of
  
  Title:Direct observation of beat-frequency switching in a self-sweeping fiber laser using variable space length
  
  Author(s):Wang, Kaile(1); Wen, Zengrun(2); Wang, Ping(3)
  Source: 2023 Opto-Electronics and Communications Conference, OECC 2023  Volume: null  Issue: null  Article Number: null  DOI: 10.1109/OECC56963.2023.10209841  Published: 2023  
  Abstract:Lately, a novel beat-frequency signal doubling In this work, we constructed a SFSSFL, where we phenomenon has been reported based on a self-sweeping fiber introduced a piece of variable space lengths using a collimator laser platform, which is essential for understanding the and mirror. We observed the RF spectra under different space mechanism of the self-sweeping effect and the wavelength lengths, and the RF peak increased as the space length interval in sweeping operation. In this work, we studied the decreased. We developed a simulation of the FSA bandwidth phenomenon using a variable space length. By controlling the to explain the switching of the beat-frequency. cavity length (also known as 'the spacing of longitudinal mode') and using a 1.8 m long fiber saturable absorber (FSA), we achieved the beat-frequency switching from the fundamental to the double frequency. Furthermore, a theoretical analysis was proposed to explain the phenomenon by calculating the reflected spectrum provided by the FSA and the change of the longitudinal mode in the cavity. © 2023 IEEE.
  Accession Number: 20233714707769
• Record 52 of
  
  Title:Secondary electron emission suppression on alumina surface and its application in multipactor suppression
  
  Author(s):Meng, Xiang-Chen(1,2,3); Wang, Dan(1); Cai, Ya-Hui(1); Ye, Zhen(4); He, Yong-Ning(1); Xu, Ya-Nan(5)
  Source: Wuli Xuebao/Acta Physica Sinica  Volume: 72  Issue: 10  Article Number: 107901  DOI: 10.7498/aps.72.20222404  Published: May 20, 2023  
  Abstract:For the high-power microwave (HPM) components applied to the space environment, the seed electrons in the components may resonate with the radio-frequency electrical field and may further lead the secondary electron multiplication to occur, triggering off the phenomenon of multipactor. Multipactor deteriorates the performance of the components, and in severe circumstances, it is even possible to result in the failure of the components or the spacecraft. Alumina ceramic possesses good dielectricity, high hardness, good thermal isolation, low dielectric loss, etc., so it is widely used in HPM systems including dielectric windows, and many other microwave components. However, alumina ceramic possesses a relatively high level of secondary electron yield (SEY or d), indicating that the devastating effect of multipactor discharge is likely to be triggered off inside the alumina-filled HPM components in the space environment. In this work, the model of alumina loaded coaxil low pass fillter is simulated to verify that reducing the SEY of the alumina surface is effective and necessary to improve the multipactor threshold. After that, we use several technologies to achieve an ultralow SEY on the alumina surface. Firstly, a series of microstructures with different porosities and aspect ratios is fabricated. The results indicate that the microstructure with 67.24% porosity and 1.57 aspect ratio shows an excellent low-SEY property, which is able to suppress the SEY peak value (dm) of alumina from 2.46 to 1.10. Then, various process parameters are used to fabricate TiN films on silicon sheets. Experimental results indicate that the TiN film achieves the lowest dm of 1.19 when the gas flow ratio of N2∶Ar is 7.5∶15. Thereafter, we deposit TiN ceramic coating onto the laser-etched microstructure samples, and an ultralow dm of 0.79 is finally achieved on alumina surface. Then we implement a qualitative analysis to explore the influence of surface charge on the secondary electron emission and multipactor for the microstructured alumina surface, discuss the mechanism of low-SEY surfaces mitigating unilateral and bilateral multipactor. For verifying the actual effect of low-SEY technologies on the suppression of multipactor, we use the technologies of constructing microstructure and depositing TiN films on the alumina surface which is filled in the designed coaxial low pass filter. Finally, we obtain a significant improvement in the multipactor threshold for the filter, which increases from 125 W to 650 W, and the improvement is 7.16 dB. This work develops an effective method to reduce SEY for alumina, which is of great scientific significance in revealing the mechanism of multipactor for the dielectric-filled microwave components and also is of engineering application significance in improving the reliability of HPM components. © 2023 Chinese Physical Society.
  Accession Number: 20232714336825
• Record 53 of
  
  Title:High-efficiency dual-layer grating coupler for vertical fiber-chip coupling in two polarizations
  
  Author(s):Li, Ke(1); Zhu, Jingping(1); Duan, Qihang(2,3); Hou, Xun(1,2)
  Source: Journal of the Optical Society of America A: Optics and Image Science, and Vision  Volume: 40  Issue: 6  Article Number: null  DOI: 10.1364/JOSAA.487739  Published: June 2023  
  Abstract:Efficient coupling between optical fibers and high-index-contrast silicon waveguides is essential for the development of integrated nanophotonics. Herein, a high-efficiency dual-layer grating coupler is demonstrated for vertical polarization-diversity fiber-chip coupling. The two waveguide layers are orthogonally distributed and designed for y- and x-polarized LP01 fiber modes, respectively. Each layer consists of two 1D stacked gratings, allowing for both perfectly vertical coupling and high coupling directionality. The gratings are optimized using the particle swarm algorithm with a preset varying trend of parameters to thin out the optimization variables. The interlayer thickness is determined to ensure efficient coupling of both polarizations. The optimized results exhibit record highs of 92% (−0.38 dB) and 85% (−0.72 dB) 3D finite-difference time-domain simulation efficiencies for y and x polarizations, respectively. The polarization-dependent loss (PDL) is below 2 dB in a 160 nm spectral bandwidth with cross talk between the two polarizations less than −24 dB. Fabrication imperfections are also investigated. Dimensional offsets of ±10 nm in etching width and ±8 nm in lateral shift are tolerated for a 1 dB loss penalty. The proposed structure offers an ultimate solution for polarization diversity coupling schemes in silicon photonics with high directionality, low PDL, and a possibility to vertically couple. © 2023 Optica Publishing Group.
  Accession Number: 20232214155289
• Record 54 of
  
  Title:Improving the Laser-Induced Breakdown Spectroscopy for Highly Efficient Trace Measurement of Hazardous Components in Waste Oils
  
  Author(s):Xu, Boping(1,2); Liu, Yinghua(1,2); Yin, Peiqi(1,2); Li, Ming(3); Zhang, Wenfu(1,2); Wang, Yishan(1,2); Zhao, Wei(1,2); Tang, Jie(1,2); Duan, Yixiang(4)
  Source: Analytical Chemistry  Volume: 95  Issue: 51  Article Number: null  DOI: 10.1021/acs.analchem.3c03579  Published: December 26, 2023  
  Abstract:Improper disposal of waste oils containing hazardous components damages the environment and the ecosystem, posing a significant threat to human life and health. Here, we present a method of discharge-assisted laser-induced breakdown spectroscopy combined with filter paper sampling (DA-LIBS-FPS) to detect hazardous components and trace the source of polluting elements. DA-LIBS-FPS significantly enhances spectral intensity by 1-2 orders of magnitude due to the discharge energy deposition into the laser-induced plasma and the highly efficient laser-sample interaction on the filter paper, when compared to single-pulse LIBS with silica wafer sampling (SP-LIBS-SWS). Additionally, the signal-to-noise ratio and the signal-to-background ratio are both significantly increased. Resultantly, indiscernible lines, such as CN and Cr I, are well distinguished. In contrast with DA-LIBS combined with silica wafer sampling (DA-LIBS-SWS), the spectral signal fluctuations in DA-LIBS-FPS are reduced by up to 33%, because of the homogeneous distribution of the oil layer on the filter paper in FPS. Further examination indicates that the limit of detection for Ba is reduced from a several parts per million level in SP-LIBS-SWS to a dozens of parts per billion level in DA-LIBS-FPS, i.e., nearly 2 orders of magnitude enhancement in analysis sensitivity. This improvement is attributed to the extended plasma lifespan in DA-LIBS and the increasing electron density and plasma temperature in FPS. DA-LIBS-FPS provides a low-cost, handy, rapid, and highly sensitive avenue to analyze the hazardous components in waste oils with great potential in environmental and ecological monitoring. © 2023 American Chemical Society.
  Accession Number: 20235115245973
• Record 55 of
  
  Title:Advanced Applications of Optical Kerr Micro-combs
  
  Author(s):Sun, Yang(1); Tan, Mengxi(2); Xu, Xingyuan(3); Wu, Jiayang(1); Li, Yang(1); Chu, Sai T.(4); Little, Brent E.(5); Morandotti, Roberto(6); Mitchell, Arnan(2); Moss, David J.(1)
  Source: 2023 Conference on Lasers and Electro-Optics, CLEO 2023  Volume: null  Issue: null  Article Number: SM1P.1  DOI: null  Published: 2023  
  Abstract:We review our work on advanced applications of optical Kerr frequency microcombs, including an optical convolutional accelerator operating at 11 Tera-OPS, as well as real-time video signal processing at a speed of 18 Terabits/s. © Optica Publishing Group 2023 © 2023 The Author(s)
  Accession Number: 20234615065684
• Record 56 of
  
  Title:End-to-end optimization of a diffractive spectral imaging system with coded aperture
  
  Author(s):Shen, Xianmeng(1,2); Ma, Suodong(1,2,3); Wang, Junxue(1,2); Yan, Qi(1,2)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12550  Issue: null  Article Number: 125500C  DOI: 10.1117/12.2666518  Published: 2023  
  Abstract:Coded aperture snapshot spectral imaging (CASSI) is an effective tool to capture spectral images, which has the advantages of snapshot imaging, high luminous flux, high signal-to-noise ratio and low sampling frequency. However, conventional CASSI generally uses refractive prisms or gratings for spectral dispersion, which leads to the nonlinear dispersion phenomenon and the requirement of large detector chip respectively. To overcome these issues, conventional refractive prisms or gratings are replaced by an axially dispersive diffractive optical element (DOE, i.e., computational optics) together with a RGB Bayer filter (i.e., a color-coded aperture) in this study. Specifically, the spatial-spectral information of a test scene is jointly modulated by the DOE and the Bayer filter integrated with a sensor chip. A fully differentiable imaging model is built based on the principle of diffractive optics and the deep learning technology. Furthermore, an optimization design of the DOE with the coded aperture is realized through an end-to-end approach, the output spectral images of which are restored by a Res-Unet neural network. Several simulation results show that up to 31 high-fidelity spectral bands in the range of 400 to 700 nm with a good spatial and spectral resolution can be recovered by the proposed snapshot system. © 2022 SPIE.
  Accession Number: 20230813601907
• Record 57 of
  
  Title:Unsupervised Transformer Boundary Autoencoder Network for Hyperspectral Image Change Detection
  
  Author(s):Liu, Song(1,2); Li, Haiwei(1); Wang, Feifei(3); Chen, Junyu(1,2); Zhang, Geng(1); Song, Liyao(4); Hu, Bingliang(1)
  Source: Remote Sensing  Volume: 15  Issue: 7  Article Number: 1868  DOI: 10.3390/rs15071868  Published: April 2023  
  Abstract:In the field of remote sens., change detection is an important monitoring technology. However, effectively extracting the change feature is still a challenge, especially with an unsupervised method. To solve this problem, we proposed an unsupervised transformer boundary autoencoder network (UTBANet) in this paper. UTBANet consists of a transformer structure and spectral attention in the encoder part. In addition to reconstructing hyperspectral images, UTBANet also adds a decoder branch for reconstructing edge information. The designed encoder module is used to extract features. First, the transformer structure is used for extracting the global features. Then, spectral attention can find important feature maps and reduce feature redundancy. Furthermore, UTBANet reconstructs the hyperspectral image and boundary information simultaneously through two decoders, which can improve the ability of the encoder to extract edge features. Our experiments demonstrate that the proposed structure significantly improves the performance of change detection. Moreover, comparative experiments show that our method is superior to most existing unsupervised methods. © 2023 by the authors.
  Accession Number: 20231613904951
• Record 58 of
  
  Title:Single Line of Sight Frame Camera Based on the Radoptic Effect of Ultrafast Semiconductor Detector
  
  Author(s):Liu, Yiheng(1,2,3); He, Kai(1); Yan, Xin(1); Gao, Guilong(1); Du, Wanyi(1); Shang, Yang(1); Wang, Gang(1); Wang, Tao(1); Zhang, Jun(4); Tian, Jinshou(1,3); Tan, Xiaobo(4)
  Source: SSRN  Volume: null  Issue: null  Article Number: null  DOI: 10.2139/ssrn.4605487  Published: October 17, 2023  
  Abstract:A new optical beam splitting method is proposed, based on which the optical frame camera capable of capturing multiple frames in a single exposure is designed and experimentally verified. The operation of the frame camera is based on an ultra-fast response semiconductor detector. It is equipped with an optical beam splitter and an optical imaging module. The ultrafast semiconductor detector receives an optical pulse that produces a transient refractive index change, and ultrafast physical processes are recorded by diffracting the probe laser through the transient phase grating. The interaction of an X-ray pulse with a semiconductor detector to produce a phase grating is simulated, based on the Monte Carlo method. The optical beam splitting mode separates a laser into two optical pulses with a certain time difference in the direction of polarization perpendicular to each other. The imaging module filters the diffracted probe laser in the spectral plane and then images multiple frames. The frame camera was used to record the temporal and spatial distribution characteristics of femtosecond laser pulses with a temporal resolution of 4.1 ps. This frame camera has great potential and value for applying to experimental studies of inertial confinement fusion. © 2023, The Authors. All rights reserved.
  Accession Number: 20230365683
• Record 59 of
  
  Title:Circularly polarized RABBIT applied to a Rabi-cycling atom
  
  Author(s):Liao, Yijie(1); Olofsson, Edvin(2); Dahlström, Jan Marcus(2); Pi, Liang-Wen(3); Zhou, Yueming(1); Lu, Peixiang(1,4)
  Source: arXiv  Volume: null  Issue: null  Article Number: null  DOI: 10.48550/arXiv.2312.12076  Published: December 19, 2023  
  Abstract:We utilize the reconstruction of attosecond beating by interference of two-photon transitions (RABBIT) technique to study the phase of a Rabi-cycling atom using circularly polarized extreme ultraviolet and infrared (IR) fields, where the IR field induces Rabi oscillations between the 2s and 2p states of lithium. Autler-Townes splittings are observed in sidebands of the photoelectron spectra and the relative phases of outgoing electron wave packets are retrieved from the azimuthal angle. In this RABBIT scheme, more ionization pathways beyond the usual two-photon pathways are required. Our results show that the polar-angle-integrated and polar-angle-resolved RABBIT phases have different behaviors when the XUV and IR fields have co- and counter-rotating circular polarizations, which are traced back to the different ionization channels according to the selection rules in these two cases and their competition relying on the propensity rule in laser-assisted photoionization. © 2023, CC BY.
  Accession Number: 20240009159
• Record 60 of
  
  Title:Generation of cylindrical vector vortex beams with high purity by using cascaded all-dielectric metasurfaces
  
  Author(s):Zhang, Xiaodong(1,2,3); Wu, Xinpeng(1); Zhang, Jili(1); Zhao, Yu(1); Ma, Ningtao(1); Mu, Qiyuan(4)
  Source: Journal of Optoelectronics and Advanced Materials  Volume: 25  Issue: 1-2  Article Number: null  DOI: null  Published: January 2023  
  Abstract:In this paper, we propose an efficient approach to generate cylindrical vector vortex beams by cascading the three all-dielectric metasurfaces. The cascaded metasurfaces are composed of 21×21 array units, operate at 1550 nm and are capable of generating the cylindrical vector vortex beams with topological charges of ±1 and polarization orders of ±1 under the incidence of circularly polarized light. Mode purity of the cylindrical vector vortex beam is 81.71% calculated by numerical simulation. Our design has characteristics of high purity, compact and easy-fabrication and may be a potential candidate in integrated optical system in future. © 2023 National Institute of Optoelectronics. All rights reserved.
  Accession Number: 20232814383992