2024

• Record 337 of
  
  Title:Snapshot compressive imaging at 855 million frames per second for aluminium planar wire array Z-pinch
  
  Author(s):Yao, Zhiming(1); Ji, Chao(2); Sheng, Liang(1); Song, Yan(1); Liu, Zhen(1); Han, Changcai(1); Zhou, Haoyu(1,3); Duan, Baojun(1); Li, Yang(1); Hei, Dongwei(1); Tian, Jinshou(2); Xue, Yanhua(2)
  Source: Optics Express  Volume: 32  Issue: 4  DOI: 10.1364/OE.512450  Published: February 12, 2024  
  Abstract:This paper present a novel, integrated compressed ultrafast photography system for comprehensive measurement of the aluminium planar wire array Z-Pinch evolution process. The system incorporates a large array streak camera and embedded encoding to improve the signal-to-noise ratio. Based on the "QiangGuang-I" pulsed power facility, we recorded the complete continuous 2D implosion process of planar wire array Z-Pinch for the first time. Our results contribute valuable understanding of imploding plasma instabilities and offer direction for the optimization of Z-Pinch facilities. © 2024 Optica Publishing Group.
  Accession Number: 20240815569617
• Record 338 of
  
  Title:Design of a refractive-metasurface hybrid annular aperture folded optical system
  
  Author(s):Mao, Shan(1,2); Lai, Tao(1); Yuan, Peiqi(1); Wang, Junzhe(1); Zhao, Jianlin(1)
  Source: Optics Express  Volume: 32  Issue: 7  DOI: 10.1364/OE.517002  Published: March 25, 2024  
  Abstract:Folded lenses offer advantages in terms of lightness and thinness, but they have limitations when it comes to correcting aberrations. In this paper, we propose a novel approach to address this issue by incorporating metasurfaces in the design of folded optical systems. Specifically, a folded refractive-metasurface hybrid annular aperture folded lens (AFL) is introduced. The structural characteristics of the AFL imaging system are analyzed to investigate the blocking ratio, thickness, and light collection capability of the ring aperture system. Additionally, a hybrid optical integration design using Zemax software is proposed for the metasurfaces. A quadruple-folded AFL working in the mid-infrared waveband is then designed. The superstructure surface is analyzed, and its processability is discussed. The results demonstrate that the reflective-metasurface hybrid AFL significantly improves the imaging quality of this type of optical system while meeting the required design accuracy. © 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
  Accession Number: 20241415835164
• Record 339 of
  
  Title:Study on the construction of twisted cosine partially coherent beams and their propagation characteristics
  
  Author(s):Zhang, Shaohua(1); Zhou, Yuan(2,3); Chai, Yutong(1); Qu, Jun(1)
  Source: AIP Advances  Volume: 14  Issue: 2  DOI: 10.1063/5.0186514  Published: February 1, 2024  
  Abstract:We propose a novel Schell model source for generating twisted partially coherent beams with an initial radius of curvature, which is called a twisted flat-topped cosine Gaussian Schell-model (TFCGSM) source. The TFCGSM beam comprises a wavefront phase and a flat-top structure, with the source degree of coherence determined by two cosine functions. Based on the Huygens-Fresnel principle, the general analytical expression of the cross-spectral density function of the TFCGSM beam propagating through the paraxial ABCD optical system is derived, and then its propagation properties are studied. The results show that the conversion of the array of the beam and the non-uniform structure can be realized by adjusting the parameters in the source plane. As the propagation distance of the TFCGSM beam increases, it rotates around the axis and increases the intensity of the array distribution. Surprisingly, the initial radius of curvature can cause the beam to rotate. The unique shape and properties of the TFCGSM beam create new possibilities for optical communication and enhanced optical functions. © 2024 Author(s).
  Accession Number: 20240815596823
• Record 340 of
  
  Title:CMID: Crossmodal Image Denoising via Pixel-Wise Deep Reinforcement Learning
  
  Author(s):Guo, Yi(1,2,3); Gao, Yuanhang(4); Hu, Bingliang(1,3); Qian, Xueming(2); Liang, Dong(4)
  Source: Sensors  Volume: 24  Issue: 1  DOI: 10.3390/s24010042  Published: January 2024  
  Abstract:Removing noise from acquired images is a crucial step in various image processing and computer vision tasks. However, the existing methods primarily focus on removing specific noise and ignore the ability to work across modalities, resulting in limited generalization performance. Inspired by the iterative procedure of image processing used by professionals, we propose a pixel-wise crossmodal image-denoising method based on deep reinforcement learning to effectively handle noise across modalities. We proposed a similarity reward to help teach an optimal action sequence to model the step-wise nature of the human processing process explicitly. In addition, We designed an action set capable of handling multiple types of noise to construct the action space, thereby achieving successful crossmodal denoising. Extensive experiments against state-of-the-art methods on publicly available RGB, infrared, and terahertz datasets demonstrate the superiority of our method in crossmodal image denoising. © 2023 by the authors.
  Accession Number: 20240215372894
• Record 341 of
  
  Title:Efficient Power Scaling of Broad-Area Laser Diodes from 915 to 1064 nm
  
  Author(s):Yang, Guowen(1,2,3); Liu, Yuxian(2,3); Zhao, Yuliang(2,3); Lan, Yu(2,3); Zhao, Yongming(1); Tang, Song(1); Wu, Wenjun(1); Yao, Zhonghui(1); Li, Ying(1); Di, Jiuwen(1); Jixiang, Lin(1); Demir, Abdullah(4)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12867  Issue:   DOI: 10.1117/12.3002642  Published: 2024  
  Abstract:Our primary goal is to significantly enhance the output power of broad-area laser diodes (LDs) for improved cost-effectiveness of laser systems and broaden their applications in various fields. To achieve this, we implemented an epitaxial design with low internal optical loss and high internal efficiency in agreement with our simulations. We present comprehensive results of high-power single-emitter and bar LDs spanning wavelengths from 915 to 1064 nm. To demonstrate power scaling in single emitter LDs, we utilized waveguide widths from 100 to 500 µm, achieving a continuous-wave (CW) maximum output power of 74 W at 976 nm under room temperature conditions, limited by the heatsink temperature control. We also build fiber-coupled modules with single-emitters operating at 1.6 kW. Employing the same epitaxial structure in 1-cm wide laser bars, we demonstrated 976 nm laser bars operated at 100 A CW with 113 W output and a high efficiency of 72.9% at room temperature. Additionally, we achieved 500 W room-temperature CW laser bars at 940 nm. For long wavelength designs at 1064 nm, 500 W output was obtained in quasi-continuous-wave (QCW) operating laser bars. Our results represent significant advancements in obtaining high power and efficient LDs across a broad wavelength range and configuration. © 2024 SPIE.
  Accession Number: 20241615941127
• Record 342 of
  
  Title:High-performance reconstruction method combining total variation with a video denoiser for compressed ultrafast imaging
  
  Author(s):Pei, Chengquan(1); Day-Uei Li, David(2); Shen, Qian(3); Zhang, Shian(4); Qi, Dalong(4); Jin, Chengzhi(4); Dong, Le(1)
  Source: Applied Optics  Volume: 63  Issue: 8  DOI: 10.1364/AO.506058  Published: March 10, 2024  
  Abstract:Compressed ultrafast photography (CUP) is a novel two-dimensional (2D) imaging technique to capture ultrafast dynamic scenes. Effective image reconstruction is essential inCUPsystems.However, existing reconstruction algorithms mostly rely on image priors and complex parameter spaces. Therefore, in general, they are time-consuming and result in poor imaging quality, which limits their practical applications. In this paper, we propose a novel reconstruction algorithm, to the best of our knowledge, named plug-in-plug-fast deep video denoising net-total variation (PnP-TV-FastDVDnet), which exploits an image’s spatial features and correlation features in the temporal dimension. Therefore, it offers higher-quality images than those in previously reported methods. First, we built a forward mathematical model of the CUP, and the closed-formsolution of the three suboptimization problems was derived according to plug-in and plug-out frames. Secondly, we used an advanced video denoising algorithm based on a neural network named FastDVDnet to solve the denoising problem. The peak signal-to-noise ratio (PSNR) and structural similarity index measure (SSIM) are improved on actual CUP data compared with traditional algorithms. On benchmark and real CUP datasets, the proposed method shows the comparable visual results while reducing the running time by96% over state-of-the-art algorithms. © 2024 Optica Publishing Group.
  Accession Number: 20241215786117
• Record 343 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 344 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 345 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 346 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 347 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 348 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