2024

• Record 85 of
  
  Title:Narrow versus Broad Waveguide Laser Diodes: A Comparative Analysis of Self-Heating and Reliability
  
  Author(s):Demir, Abdullah(1); Sünnetçioğlu, Ali Kaan(1); Ebadi, Kaveh(1); Liu, Yuxian(2,3); Tang, Song(4); Yang, Guowen(2,3,4)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12867  Issue:   DOI: 10.1117/12.3002971  Published: 2024  
  Abstract:Semiconductor laser diodes (LDs) generate high output powers with high power conversion efficiencies. While broad-area LDs are favored for high-power applications, narrow-waveguide LDs are in demand for their single-mode characteristics. However, LDs suffer from device failures caused by catastrophic optical damage (COD) due to elevated self-heating at high operating currents. It is critical to understand the COD mechanism in these devices to enhance their reliability and operating output power. In this study, we investigated the self-heating and temperature characteristics of LDs with varying waveguide widths to uncover the cause of their failure mechanism. We assessed the performance, junction, and facet temperatures of the narrow (W=7 µm) and broad waveguide (W=100 µm) LDs. The narrower waveguide LDs achieved and operated at higher output power densities but, surprisingly, maintained lower junction and facet temperatures. Additionally, we employed a thermal simulation model to analyze heat transport characteristics versus LD waveguide widths. The simulation results showed that narrower waveguide LDs exhibit improved three-dimensional heat dissipation, resulting in reduced junction and facet temperatures and, thus, enhanced reliability. Our simulations align well with the experimental data. The findings demonstrate a transition in heat dissipation characteristics from broad to narrow waveguide behavior at approximately 50 µm width. These results clarify the fundamental reasons behind the superior reliability of narrower waveguide LDs and provide valuable guidance for LD thermal management. © 2024 SPIE.
  Accession Number: 20241615941113
• Record 86 of
  
  Title:Kerr Optical Frequency Comb Evolution in a Gain Fiber Cavity Embedded with a Microresonator
  
  Author(s):Liu, Ziyu(1,3); Wang, Gang(1,3); Tian, Jinshou(1); Lou, Rui(2); Shen, Jun(2); Wang, Weiqiang(2); Zhao, Wei(2)
  Source: SSRN  Volume:   Issue:   DOI: 10.2139/ssrn.4765422  Published: March 19, 2024  
  Abstract:Microcavity-based frequency combs, or ‘microcombs’ have enabled many fundamental breakthroughs of cavity optical physics during the last decade, which also show excellent values in many application fields. In this paper, we experimentally demonstrate Kerr optical frequency comb evolution in a gain fiber cavity embedded with a high-Q micro-ring resonator. Through tuning the pump power and polarization state, single frequency laser, mode-locked laser (primary-comb-like), bunched sub-combs, phase-locked comb and high-noise combs are observed in sequence. The proposed scheme is low power consumption as the optical frequency combs are formed by stimulated emission in a gain cavity and phase locked by thresholdless four wave mixing effect in a micro-resonator. The proposed optical frequency comb exhibits excellent thermal stability for the intrinsic feedback mechanism. Further, our scheme has the potential to realize full integration by replacing the fiber devices with semiconductor components. © 2024, The Authors. All rights reserved.
  Accession Number: 20240116387
• Record 87 of
  
  Title:High accuracy ranging for space debris with spaceborne single photon Lidar
  
  Author(s):Tian, Yuan(1,2,3,4); Hu, Xiaodong(2); Chen, Songmao(1,2,4); Zhao, Yixin(1,2,3,4); Zhang, Xuan(1,2,3,4); Wang, Dingjie(1,2,3,4); Xu, Weihao(1,2,3,4); Xie, Meilin(1,2,4); Hao, Wei(1,2,4); Su, Xiuqin(1,2,4)
  Source: Optics Express  Volume: 32  Issue: 7  DOI: 10.1364/OE.519002  Published: March 25, 2024  
  Abstract:The increasing risk posed by space debris highlights the need for accurate localization techniques. Spaceborne single photon Lidar (SSPL) offers a promising solution, overcoming the limitations of traditional ground-based systems by providing expansive coverage and superior maneuverability without being hindered by weather, time, or geographic constraints. This study introduces a novel approach leveraging non-parametric Bayesian inference and the Dirichlet process mixture model (DPMM) to accurately determine the distance of space debris in low Earth orbit (LEO), where debris exhibits nonlinear, high dynamic motion characteristics. By integrating extended Kalman filtering (EKF) for range gating, our method captures the temporal distribution of reflected photons, employing Markov chain Monte Carlo (MCMC) for iterative solutions. Experimental outcomes demonstrate our method s superior accuracy over conventional statistical techniques, establishing a clear correlation between radial absolute velocity and ranging error, thus significantly enhancing monostatic space debris localization. © 2024 Optica Publishing Group (formerly OSA). All rights reserved.
  Accession Number: 20241415837511
• Record 88 of
  
  Title:Methodology and Modeling of UAV Push-Broom Hyperspectral BRDF Observation Considering Illumination Correction
  
  Author(s):Wang, Zhuo(1,2); Li, Haiwei(1); Wang, Shuang(1,3); Song, Liyao(4); Chen, Junyu(1)
  Source: Remote Sensing  Volume: 16  Issue: 3  DOI: 10.3390/rs16030543  Published: February 2024  
  Abstract:The Bidirectional Reflectance Distribution Function (BRDF) is a critical spatial distribution parameter in the quantitative research of remote sensing and has a wide range of applications in radiometric correction, elemental inversion, and surface feature estimation. As a new means of BRDF modeling, UAV push-broom hyperspectral imaging is limited by the push-broom imaging method, and the multi-angle information is often difficult to obtain. In addition, the random variation of solar illumination during UAV low-altitude flight makes the irradiance between different push-broom hyperspectral rows and different airstrips inconsistent, which significantly affects the radiometric consistency of BRDF modeling and results in the difficulty of accurately portraying the three-dimensional spatial reflectance distribution in the UAV model. These problems largely impede the application of outdoor BRDF. Based on this, this paper proposes a fast multi-angle information acquisition scheme with a high-accuracy BRDF modeling method considering illumination variations, which mainly involves a lightweight system for BRDF acquisition and three improved BRDF models considering illumination corrections. We adopt multi-rectangular nested flight paths for multi-gray level targets, use multi-mode equipment to acquire spatial illumination changes and multi-angle reflectivity information in real-time, and introduce the illumination correction factor K through data coupling to improve the kernel, Hapke, and RPV models, and, overall, the accuracy of the improved model is increased by 20.83%, 11.11%, and 31.48%, respectively. The results show that our proposed method can acquire multi-angle information quickly and accurately using push-broom hyperspectral imaging, and the improved model eliminates the negative effect of illumination on BRDF modeling. This work is vital for expanding the multi-angle information acquisition pathway and high-efficiency and high-precision outdoor BRDF modeling. © 2024 by the authors.
  Accession Number: 20240715549174
• Record 89 of
  
  Title:Two-dimensional numerical simulation of pre-ionized direct-current glow discharge in atmospheric helium*
  
  Author(s):Liu, Zai-Hao(1,2); Liu, Ying-Hua(1,2); Xu, Bo-Ping(1,2); Yin, Pei-Qi(1,2); Li, Jing(3); Wang, Yi-Shan(1,2); Zhao, Wei(1,2); Duan, Yi-Xiang(4); Tang, Jie(1,2)
  Source: Wuli Xuebao/Acta Physica Sinica  Volume: 73  Issue: 1  DOI: 10.7498/aps.73.20230712  Published: January 5, 2024  
  Abstract:In this paper, the effect of pre-ionization on the small-gap and large-gap direct-current glow discharge at atmospheric pressure are investigated based on a two-dimensional self-consistent fluid model. For both the discharges, the results show that with the enhancement of pre-ionization, the charged particle distribution gradually shifts toward the cathode along the discharge direction, making the cathode fall zone shrink continuously. The width of the positive column region, negative glow space, and cathode fall zone continuously extend along the vertical discharge direction, and the distribution of electron density and ion density are more uniform. For the electric field, with the enhancement of pre-ionization, the longitudinalal component distribution of the electric field in the cathode fall zone gradually contracts toward the cathode, and the overall electric field near the cathode decreases and becomes more uniformly distributed. The transverse component distribution of the electric field gradually decreases and shrinks toward the wall. The overall electron temperature in the discharge space decreases with the enhancement of the pre-ionization level, and the electron temperature distribution in the cathode fall zone gradually shrinks toward the cathode. In addition, the overall potential of the discharge space also decreases. The introduction of pre-ionization significantly reduces the maintaining voltage and discharge power of the direct-current glow discharge. Furthermore, the potential drop in the small-gap discharge is always concentrated in the cathode fall zone as the pre-ionization increases, while the potential drop in the large-gap discharge is gradually shifted from the cathode fall zone to the positive column region. This simulation shows that the pre-ionization not only effectively enhances the discharge uniformity, but also largely reduces the maintaining voltage and energy consumption of the direct-current glow discharge. This work is an important guideline for further optimizing the electrode configuration and the operating parameters of the plasma source. © 2024 Institute of Physics, Chinese Academy of Sciences. All rights reserved.
  Accession Number: 20240815605290
• Record 90 of
  
  Title:Spectroscopic Mueller Metrix Polarimetry Based on Spectral Modulation and Division of Amplitude Demodulation
  
  Author(s):Deng, Zhongxun(1,2); Quan, Naicheng(2); Li, Siyuan(3); Zhang, Chunmin(4)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 53  Issue: 4  DOI: 10.3788/gzxb20245304.0430004  Published: April 2024  
  Abstract:Thin film and nanostructure measurement technologies have played an important role in production process monitoring in industries such as integrated circuit manufacturing, flat panel displays, and solar cells. Many optical based measurement techniques have emerged to meet the industrial needs of high-speed and nondestructive measurement. Spectroscopic Mueller Metrix Polarimetry(SMMP)is a typical representative of these techniques and has become an important direction in the research and development of thin film and nanostructure measurement technology. It uses a Polarization State Generator(PSG)to convert a certain spectral range of polychromatic light into fully polarized light and project it onto the surface of the sample to be tested, and uses the Polarization State Analyzer(PSA)to detect the polarization state of the reflected or transmitted light on the surface of the sample for obtaining all 16 Mueller matrix elements of the sample as a function of wavelength, and then analyzes and extracts their characteristic parameters such as complex dielectric constant, carrier structure, and film thickness. SMMP can be divided into frequency modulation type and time modulation type according to its working principle. The polarization state generator and polarization state analyzer of the former are both composed of components that can change modulation parameters over time and fixed linear polarizers, such as rotary compensators, liquid crystal phase delay devices, and photoblastic modulators. When measuring in a wide spectral range, the SMMP with dual rotation compensators is the most common:the compensators of PSG and PSA rotate at a certain rate to produce different time modulation frequencies, and then use Fourier transform demodulation to obtain all 16 Mueller matrix elements of the sample, which takes a long measurement time and is not suitable for situations where Mueller matrix elements change rapidly over time;The PSG and PSA of the latter are both composed of two high-order phase delay devices configured with a certain thickness and fixed fast axis direction, as well as a fixed linear polarizer. All 16 elements of the measured Mueller matrix are modulated to 37 different frequency channels, and the spectra of all 16 Mueller matrix elements can be obtained by channel filtering and Fourier transform. As the system does not contain moving components, static real-time measurement can be achieved. However, when the light source or the measured Mueller matrix has sharp characteristic peaks, serious channel crosstalk will occur, which affects measurement accuracy and accuracy. According to the principle of Fourier transform spectroscopy, a large channel bandwidth corresponds to high restoration spectral resolution. Due to the limited total channel bandwidth, an increase in the number of channels will reduce the bandwidth required to restore the Muller matrix spectrum. Therefore, the spectral resolution of the measured Mueller matrix elements is much smaller than the spectral resolution of the spectrometer. Therefore, it is only suitable for situations where the measured Mueller matrix slowly changes with wavelength. To overcome these limitations, we presented a SMMP based on frequency modulation and division of amplitude demodulation. Compared with the spectroscopic Mueller polarimetry based on time modulation or frequency-temporal modulation, it has no moving components and electronic devices, and can achieve real-time measurement of the spectra of all 16 Mueller matrix elements of the sample. Compared with the spectroscopic Mueller polarimetry based on frequency modulation, it has higher spectral resolution and lower the probability of channel crosstalk generation. According to the research results, the selection of high-order retarders and spectrometers can further expand the spectral range of measurement. By optimizing the calibration method, the accuracy and precision of optical measurement can be further improved. This article has certain scientific significance and potential application prospects in the research and development of high-speed, high-precision, and wide spectral band generalized spectral ellipsometry technology in the field of non-destructive testing technology. © 2024 Chinese Optical Society. All rights reserved.
  Accession Number: 20241715962743
• Record 91 of
  
  Title:Optimization of signal-to-noise ratio of laser heterodyne radiometer
  
  Author(s):Sun, Chunyan(1,2,3); He, Xinyu(1); Xu, Ruoyu(1); Lu, Sifan(1); Pan, Xueping(1); Bai, Jin(1)
  Source: Microwave and Optical Technology Letters  Volume: 66  Issue: 1  DOI: 10.1002/mop.33857  Published: January 2024  
  Abstract:The ground-based laser heterodyne radiometer (LHR), which exhibits the advantages of small size, high spectral resolution, and easy integration, has been used for the remote sensing detection of several gases to meet a wide range of needs. This study aims to optimize the laser heterodyne system for detecting CO2 gas by focusing on existing research. Firstly, using the all-fiber laser heterodyne detection system built by our research group, the power spectrum associated with the radio frequency signals of the detection system is discussed under different conditions: under no irradiation, under sunlight only, under sunlight and laser irradiation at the absorption peak, and under a filter in the spectrum range of 185–270 MHz. Signal-to-noise ratios (SNRs) of the high-resolution spectrum have been obtained using different filter bands of 185–270, 225–270, and 225–400 MHz. Finally, the filter in the 225–270 MHz band, which has the highest SNR, is selected. Consequently, the resolution is improved and the system is further optimized. Furthermore, an optical fiber attenuator is used to change the power of the local oscillator light entering the system, and hyperspectral spectra with varying percentages of input energy and total energy are obtained. When the laser attenuation reaches 40%, the optimal SNR of the system is 486 and can be further improved to meet the expected requirements. This study will provide insights for improving the applicability of laser heterodyne technology in atmospheric sounding. © 2023 Wiley Periodicals LLC.
  Accession Number: 20233714728857
• Record 92 of
  
  Title:Generation of arbitrarily structured optical vortex arrays based on the epicycle model
  
  Author(s):Yuping, T.A.I.(1,2); Haihao, F.A.N.(1); Xin, M.A.(1); Wenjun, W.E.I.(1); Zhang, Hao(1); Tang, Miaomiao(1); Xinzhong, L.I.(1,2,3)
  Source: Optics Express  Volume: 32  Issue: 6  DOI: 10.1364/OE.521250  Published: March 11, 2024  
  Abstract:Optical vortex arrays (OVAs) are complex light fields with versatile structures that have been widely studied in large-capacity optical communications, optical tweezers, and optical measurements. However, generating OVAs with arbitrary structures without explicit analytical expressions remains a challenge. To address this issue, we propose an alternative scheme for customizing OVAs with arbitrary structures using an epicycle model and vortex localization techniques. This method can accurately generate an OVA with an arbitrary structure by predesigning the positions of each vortex. The influence of the number and coordinates of the locating points on customized OVAs is discussed. Finally, the structures of the OVA and each vortex are individually shaped into specifically formed fractal shapes by combining cross-phase techniques. This unique OVA will open up novel potential applications, such as the complex manipulation of multiparticle systems and optical communication based on optical angular momentum. © 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
  Accession Number: 20241215766416
• Record 93 of
  
  Title:Depth-Resolved Imaging Through Dynamic Scattering Media Via Speckle Cross-Correlation Under Near-Infrared Illumination
  
  Author(s):Wang, Ping(1,2); Zhou, Meiling(2); Zhang, Yang(2,3); Li, Runze(2); Peng, Tong(2); Zhou, Yuan(2,3); Min, Junwei(2); Yao, Cuiping(1); Yao, Baoli(2,3)
  Source: SSRN  Volume:   Issue:   DOI: 10.2139/ssrn.4690404  Published: January 10, 2024  
  Abstract:Speckle cross-correlation imaging (SCCI) method has the depth-resolved capability, benefiting from the introduction of a reference point. However, the quality of the reconstructed image is severely degraded due to the background noise, which becomes more prominent when imaging through dynamic scattering media. Here, we propose a composite-differential filter-assisted speckle cross-correlation imaging (CDF-SCCI) method, allowing for effectively reducing the background noise of the reconstructed image. The CDF-SCCI method can increase the reconstructed image contrast by a factor of 5. A speckle cross-correlation based imaging system under near-infrared (NIR) illumination is built to enhance the imaging quality further. Quantitative comparison of the reconstructed results through dynamic media with different optical depths reveals the superiority of the NIR illumination over the visible light illumination, extending the maximum optical depth from 7.7 to 10.4. The depth-resolved imaging through various dynamic media, including the SiO2 suspension, milk and anticoagulated pig blood, further demonstrates the potential application of the proposed CDF-SCCI method under NIR illumination in biomedical imaging. © 2024, The Authors. All rights reserved.
  Accession Number: 20240035370
• Record 94 of
  
  Title:Attention Network with Outdoor Illumination Variation Prior for Spectral Reconstruction from RGB Images
  
  Author(s):Song, Liyao(1); Li, Haiwei(2); Liu, Song(3); Chen, Junyu(2); Fan, Jiancun(4); Wang, Quan(2); Chanussot, Jocelyn(5)
  Source: Remote Sensing  Volume: 16  Issue: 1  DOI: 10.3390/rs16010180  Published: January 2024  
  Abstract:Hyperspectral images (HSIs) are widely used to identify and characterize objects in scenes of interest, but they are associated with high acquisition costs and low spatial resolutions. With the development of deep learning, HSI reconstruction from low-cost and high-spatial-resolution RGB images has attracted widespread attention. It is an inexpensive way to obtain HSIs via the spectral reconstruction (SR) of RGB data. However, due to a lack of consideration of outdoor solar illumination variation in existing reconstruction methods, the accuracy of outdoor SR remains limited. In this paper, we present an attention neural network based on an adaptive weighted attention network (AWAN), which considers outdoor solar illumination variation by prior illumination information being introduced into the network through a basic 2D block. To verify our network, we conduct experiments on our Variational Illumination Hyperspectral (VIHS) dataset, which is composed of natural HSIs and corresponding RGB and illumination data. The raw HSIs are taken on a portable HS camera, and RGB images are resampled directly from the corresponding HSIs, which are not affected by illumination under CIE-1964 Standard Illuminant. Illumination data are acquired with an outdoor illumination measuring device (IMD). Compared to other methods and the reconstructed results not considering solar illumination variation, our reconstruction results have higher accuracy and perform well in similarity evaluations and classifications using supervised and unsupervised methods. © 2023 by the authors.
  Accession Number: 20240315384638
• Record 95 of
  
  Title:Repetition rate tuning and locking of solitons in a microrod resonator
  
  Author(s):Niu, Rui(1,2); Wan, Shuai(1,2); Sun, Shu-Man(1,2); Ma, Tai-Gao(1,2); Chen, Hao-Jing(1,2); Wang, Wei-Qiang(3,4); Lu, Zhizhou(3,4); Zhang, Wen-Fu(3,4); Guo, Guang-Can(1,2); Zou, Chang-Ling(1,2); Dong, Chun-Hua(1,2)
  Source: Optics Letters  Volume: 49  Issue: 3  DOI: 10.1364/OL.511339  Published: February 2024  
  Abstract:Recently, there has been significant interest in the generation of coherent temporal solitons in optical microresonators. In this Letter, we present a demonstration of dissipative Kerr soliton generation in a microrod resonator using an auxiliary-laser-assisted thermal response control method. In addition, we are able to control the repetition rate of the soliton over a range of 200 kHz while maintaining the pump laser frequency, by applying external stress tuning. Through the precise control of the PZT voltage, we achieve a stability level of 3.9 × 10−10 for residual fluctuation of the repetition rate when averaged 1 s. Our platform offers precise tuning and locking capabilities for the repetition frequency of coherent mode-locked combs in microresonators. This advancement holds great potential for applications in spectroscopy and precision measurements. © 2024 Optica Publishing Group.
  Accession Number: 20240615521839
• Record 96 of
  
  Title:All-optical neural network nonlinear activation function based on the optical bistability within a micro-ring resonator
  
  Author(s):Zhang, Hui(1); Wen, Jin(1,2); Wu, Zhengwei(1); Wang, Qian(1); Yu, Huimin(1); Zhang, Ying(1); Pan, Yu(1); Yin, Lan(1); Wang, Chenglong(1); Qu, Shuangchao(1)
  Source: Optics Communications  Volume: 558  Issue:   DOI: 10.1016/j.optcom.2024.130374  Published: May 1, 2024  
  Abstract:Training all-optical neural networks in itself remains an unresolved problem, and the challenges compound when the problem is turned into the hardware implementations. In this paper, we propose a nonlinear activation function based on optical bistability within a micro-ring resonator (MRR), achieving threshold control without external modulation. Furthermore, a convolutional neural network similar to the Le-Net-5 architecture is designed, in which all nonlinear activation functions are composed of optical bistable hysteresis loop. The numerical simulation results demonstrate that the recognition rate on the Fashion-MNIST dataset can achieve 91.3%, which means that the optical neuromorphic computation can be implemented by utilizing the nonlinear optical effects themselves in the all-optical hardware. Such a scheme promises access to the all-optical neural network training in the optical hardware environment compared to numerical activation functions. © 2024 Elsevier B.V.
  Accession Number: 20240815608927