2022

• Record 25 of
  
  Title:Rocket active drift measurement technology based on lidar
  
  Author(s):Shi, Heng(1,2,3); Gao, Xin(1); Li, Xiyu(1); Lei, Chengqiang(1); Hu, Lei(1); Zong, Yonghong(1); Zheng, Donghao(1); Tang, Jia(1)
  Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering  Volume: 51  Issue: 7  DOI: 10.3788/IRLA20210636  Published: July 2022  
  Abstract:In view of the problems existing in the current high-speed TV rendezvous measurement of rocket drift, such as the great influence of the external environment and the inability to obtain the measurement data in real time, an active measurement method of rocket takeoff real-time drift based on lidar is proposed. First, the lidar is installed on the two-dimensional precision turntable through the installation platform. In the process of rocket launch, the two-dimensional precision turntable drives the lidar to continuously track and scan the target point position of the rocket with high precision, and obtain the lidar point cloud data corresponding to the target point position. Then, the data processing system receives the lidar point cloud data, fits the elliptical curve and the elliptical curve center point of each frame data, takes the position of the elliptical center point when the rocket is stationary as the reference position, calculates the relative difference between the elliptical center point position of each frame data and the reference position, and determines the real-time drift of the rocket in the take-off stage. Finally, the measurement system and method are verified by the rocket launch test, and the test results show that under the condition of environmental interference, the measurement accuracy of real-time drift is 3.1 cm. It is the most accurate measurement method in the rocket drift measurement at present. At the same time, it can ensure the real-time performance of the data, provide real-time discrimination data for the rocket launch security console, and ensure the safety of the launch process. © 2022 Chinese Society of Astronautics. All rights reserved.
  Accession Number: 20223712723129
• Record 26 of
  
  Title:Fluid-Thermal Interaction Simulation of a Hypersonic Aircraft Optical Dome
  
  Author(s):Wang, Zhiqiang(1); Zhang, Anjing(2); Pan, Jia(1); Lu, Weiguo(1); Sun, Yubiao(3)
  Source: Energies  Volume: 15  Issue: 22  DOI: 10.3390/en15228619  Published: November 2022  
  Abstract:Hypersonic aircraft design is an enabling technology. However, many problems are encountered, including the design of the hood. The aircraft optical dome can become heated due to aerodynamic effects. Since the optical dome of a hypersonic aircraft should satisfy optical imaging requirements, a conventional ablative coating cannot be adopted. The aerodynamic heating characteristics during the whole flight must be studied. In this study, a numerical simulation method for the aerodynamic heat of hypersonic aircraft under long-term variable working conditions is proposed. In addition, the numerical simulation of the external flow field and structure coupling of the aerodynamic heat problem is performed. The dynamic parameters of temperature and pressure are obtained, and the thermal protection basis of the internal equipment is obtained. Numerical results indicate that the average temperature and maximum temperature of the optical dome for inner and outer walls exhibit an "M" shape with time, with two high-temperature cusps and one low-temperature cusp. The time of average temperature coincides with that of maximum wall temperature. During the flight, the wall pressure changes with time, exhibiting the characteristics of higher temperature at both ends of the flight and lower temperature in the middle. The structural temperature of the hypersonic aircraft is higher than that of the external flow behind the shock wave after 310 s. Therefore, this study provides a reliable reference for the preliminary design and parameter research of optical domes of hypersonic aircraft. © 2022 by the authors.
  Accession Number: 20224813183598
• Record 27 of
  
  Title:All-optical sampling of ultrashort laser pulses based on perturbed transient grating
  
  Author(s):Huang, Pei(1); Yuan, Hao(1,2); Cao, Huabao(1,2); Wang, Hushan(1,2); Wang, Xianglin(1,2); Wang, Yishan(1,2); Zhao, Wei(1,2); Fu, Yuxi(1,2)
  Source: Optics Letters  Volume: 47  Issue: 20  DOI: 10.1364/OL.473294  Published: October 15, 2022  
  Abstract:We propose and demonstrate an all-optical pulse sampling technique based on the transient grating (TG) procedure with perturbation, which provides a simple and robust manner to characterize an ultrashort laser pulse without employing a retrieval algorithm. In our approach, a two-orders weaker perturbation pulse perturbs the diffracted pulse from the TG, which is generated by another strong fundamental pulse. The modulation of the diffracted pulse energy directly represents the temporal profile of the perturbation pulse. We have successfully characterized few-cycle and multi-cycle pulses, which is consistent with the results verified by the widely employed frequency-resolved optical gating (FROG) method. Our method provides a potential way to characterize ultrashort laser waveform from the deep-UV to far-infrared region. © 2022 Optica Publishing Group.
  Accession Number: 20224613098875
• Record 28 of
  
  Title:Multi-Section Waveguide Method for Facet Temperature Reduction and Improved Reliability of High-Power Laser Diodes
  
  Author(s):Ebadi, Kaveh(1); Liu, Yuxian(2,3); Sünnetçioğlu, Ali Kaan(1); Gündoğdu, Sinan(1); Şengül, Serdar(1); Zhao, Yuliang(2,3); Lan, Yu(2,3); Yang, Guowen(2,3,4); Demir, Abdullah(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12141  Issue:   DOI: 10.1117/12.2621651  Published: 2022  
  Abstract:Catastrophic optical mirror damage (COMD) limits the output power and reliability of lasers diodes (LDs). Laser self-heating together with facet absorption of output power cause the facet to reach a critical temperature (Tc), resulting in COMD and irreversible device failure. The self-heating of the laser contributes significantly to the facet temperature, but it has not been addressed so far. We implement a multi-section waveguide method where the heat is separated from reaching the output facet by exploiting an electrically isolated window. The laser waveguide is divided into two electrically isolated laser and transparent window sections. The laser section is pumped at high current levels to achieve laser output, and the passive waveguide is biased at low injection currents to obtain a transparent waveguide with negligible heat generation. Using this design, we demonstrate facet temperatures lower than the junction temperature of the laser even at high output power operation. While standard LDs show COMD failures, the multi-section waveguide LDs are COMD-free. Our technique and results provide a pathway for high-reliability LDs, which would find diverse applications in semiconductor lasers. © 2022 SPIE.
  Accession Number: 20222612302379
• Record 29 of
  
  Title:Stray Light Characteristics and Suppression in Space-borne Doppler Asymmetric Spatial Heterodyne Interferometer
  
  Author(s):Li, Junjie(1,2); Sun, Jian(1); Zhao, Hengxiang(1); Chang, Chenguang(1,2); Fu, Di(1,2); Zhao, Hao(1); Bai, Lu(3); Feng, Yutao(1)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 51  Issue: 11  DOI: 10.3788/gzxb20225111.1130002  Published: November 2022  
  Abstract:Wind detection in middle and upper atmosphere is an important way to characterize atmospheric environment and atmospheric dynamics， which is significant for accurate weather forecast and smooth operation of aerospace missions. Satellite remote sensing of the atmospheric wind field is not limited by weather and geographical conditions， and can be used for global all-weather remote sensing observation. More importantly， using limb viewing geometry can provide long-term observation results of the global horizontal wind field and temperature distribution， which is necessary for studying large-scale and long-term space climate. Compared with Michelson interferometer and Fabry-Perot interferometer， the Doppler asymmetric spatial heterodyne interferometer has higher sensitivity， no moving parts and lower processing accuracy requirements. These advantages can greatly improve the performance of the system， and are very suitable for wind field detection activities in the middle and upper atmosphere. The space-borne wind interferometer is designed to detect the weak airglow emissions employing limb viewing geometry， which can be easily affected by background radiation from the lower atmosphere. The earth's atmosphere is composed of a variety of gases and aerosol particles. These components enable the atmosphere to absorb and scatter the incident solar radiation， which constitutes the atmospheric background radiation. The stray light will degrade the quality of the original interferogram data， decreasing the contrast and effective signal-to-noise ratio. This paper uses a satellite based on 500 km orbital altitude to measure the winds in the middle atmosphere at the height of 60~90 km， and the typical atmospheric background radiation and airglow radiation intensity are selected. The detection range of the above loads is in the upper atmosphere， and the observation of wind field in the middle atmosphere （60~90 km） will put forward higher requirements for the suppression of stray light. In addition， the multistage diffraction energy of Doppler interferometer should be analyzed. According to the atmospheric background radiation intensity at different altitudes， combined with the optical system parameters， the baffle is designed. The primary purpose of the baffle is the suppression of signal that originates from angles outside the field of view since the illuminated earth’s disk and the sun represent light sources that are many orders of magnitude brighter than the targeted airglow emissions， and during the day， the bright earth is always close to the fields of view. The adopted criterion is that the entrance aperture in front of the first lens should not receive light directly from the sunlit cloud tops， which is assumed to be 20 km altitude. In order to suppress the stray light in the field of view， the optical system is simulated to find the key surfaces which can cause the ghost image in the interferometer and the suppression structure is made. For the stray light of the interferometer multistage diffraction， simulation of rays tracing is taken to evaluate the influence on imaging. In order to evaluate the stray light suppression effect， point source transmittance analysis and illumination simulation are taken. The point source transmittance is the ratio of the illuminance at the image surface to the illuminance at the entrance pupil. The image surface illuminance map is obtained by simulating the airglow light source and the atmospheric background radiation light source. Through point source transmittance analysis and illumination simulation， the following conclusions are obtained. First， in the horizontal and diagonal directions， the point source transmittance drops below 10-5 at 0.2° outside the field of view， and in the vertical direction， the point source transmittance drops below 10-5 at 0.04° outside the field of view. Second， the atmospheric background radiation and ghost image account for 1.35% of the total energy of the image. The results show that the proposed stray light suppression method is effective and meets the requirements of the satellite-borne Doppler asymmetric spatial heterodyne interferometer. © 2022 Chinese Optical Society. All rights reserved.
  Accession Number: 20224513074945
• Record 30 of
  
  Title:Generalized Scene Classification From Small-Scale Datasets With Multitask Learning
  
  Author(s):Zheng, Xiangtao(1); Gong, Tengfei(2,3); Li, Xiaobin(4); Lu, Xiaoqiang(5)
  Source: IEEE Transactions on Geoscience and Remote Sensing  Volume: 60  Issue:   DOI: 10.1109/TGRS.2021.3116147  Published: 2022  
  Abstract:Remote sensing images contain a wealth of spatial information. Efficient scene classification is a necessary precedent step for further application. Despite the great practical value, the mainstream methods using deep convolutional neural networks (CNNs) are generally pretrained on other large datasets (such as ImageNet) and thus fail to capture the specific visual characteristics of remote sensing images. For another, it lacks the generalization ability to new tasks when training a new CNN from scratch with an existing remote sensing dataset. This article addresses the dilemma and uses multiple small-scale datasets to learn a generalized model for efficient scene classification. Since the existing datasets are heterogeneous and cannot be directly combined to train a network, a multitask learning network (MTLN) is developed. The MTLN treats each small-scale dataset as an individual task and uses complementary information contained in multiple tasks to improve generalization. Concretely, the MTLN consists of a shared branch for all tasks and multiple task-specific branches with each for one task. The shared branch extracts shared features for all tasks to achieve information sharing among tasks. The task-specific branch distills the shared features into task-specific features toward the optimal estimation of each specific task. By jointly learning shared features and task-specific features, the MTLN maintains both generalization and discrimination abilities. Two types of MTL scenarios are explored to validate the effectiveness of the proposed method: one is to complete multiple scene classification tasks and the other is to jointly perform scene classification and semantic segmentation. 1558-0644 © 2021 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See https://www.ieee.org/publications/rights/index.html for more information.
  Accession Number: 20214211038001
• Record 31 of
  
  Title:Advances in Silica-Based Large Mode Area and Polarization-Maintaining Photonic Crystal Fiber Research
  
  Author(s):Ma, Yuan(1,2); Wan, Rui(1,2); Li, Shengwu(1,2); Yang, Liqing(1); Wang, Pengfei(1,2)
  Source: Materials  Volume: 15  Issue: 4  DOI: 10.3390/ma15041558  Published: February-2 2022  
  Abstract:In recent years, photonic crystal fibers (PCFs) have attracted increasing attention. Compared with traditional optical fibers, PCFs exhibit many unique optical properties and superior performance due to their high degree of structural design freedom. Using large-mode area (LMA) fibers with single-mode operation is essential to overcoming emerging problems as the power of fiber lasers scales up, which can effectively reduce the power density and mitigate the influence of nonlinear effects. With a brief introduction of the concept, classification, light transmission mechanism, basic properties, and theoretical analysis methods of PCFs, this paper mainly compiles the worldwide development of large-mode area and polarization-maintaining (PM) PCFs, and finally proposes possible technical routes to realize the single-mode operation of LMA-PCFs and PM-LMA-PCFs. Finally, the future development prospects of the PCFs are discussed. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
  Accession Number: 20220811698622
• Record 32 of
  
  Title:150 Gbit/s 1 km high-sensitivity FSO communication outfield demonstration based on a soliton microcomb
  
  Author(s):Jia, Shuaiwei(1,2,3); Xie, Zhuang(1,2,3); Shao, Wen(1,2,3); Wang, Yang(1,2,3); He, Yuanchen(1); Zhang, Dongquan(1); Liao, Peixuan(1,3); Wang, Weiqiang(1); Gao, Duorui(1,3); Wang, Wei(1); Xie, Xiaoping(1,2,3)
  Source: Optics Express  Volume: 30  Issue: 20  DOI: 10.1364/OE.465803  Published: September 26, 2022  
  Abstract:A high-sensitivity and large-capacity free space optical (FSO) communication scheme based on the soliton microcomb (SMC) is proposed. Using ultra-large bandwidth stabilized SMC with a frequency interval of 48.97 GHz as the laser source, 60 optical wavelengths modulated by 2.5 Gbit/s 16-Pulse position modulation (PPM) are transmitted in parallel. A corresponding outfield high-sensitivity 150 Gbit/s FSO communication experiment based on the SMC was carried out with 1 km space distance. Our experimental results show that the best sensitivity of the single comb wavelength which has higher OSNR can reach −52.62 dBm, and the difference is only 1.38 dB from the theoretical limit under the BER of 1 × 10−3 without forward error correction (FEC). In addition, at BER of 1 × 10−3, 16-PPM has a higher received sensitivity of 6.73dB and 3.72dB compared to on-off keying (OOK) and differential phase shift keying (DPSK) respectively. Meanwhile, taking the advantage of multi-channel SMC, 60 × 2.5 Gbit/s can achieve 150 Gbit/s large-capacity free-space transmission. For comparison, commercially available single-wavelength laser based FSO communication system have also been performed in the outfield. The outfield experimental results demonstrated the feasibility of high-sensitivity, large-capacity PPM FSO communication based on SMCs and provided a new perspective for the future development of large-capacity, long-haul FSO communication. © 2022 Optica Publishing Group.
  Accession Number: 20223912797421
• Record 33 of
  
  Title:Fast non-line-of-sight imaging based on product-convolution expansions
  
  Author(s):Xu, Weihao(1,2); Chen, Songmao(1,3); Tian, Yuyuan(1,2); Wang, Dingjie(1,2); Su, Xiuqin(1,3)
  Source: Optics Letters  Volume: 47  Issue: 18  DOI: 10.1364/OL.469719  Published: September 15, 2022  
  Abstract:Non-line-of-sight (NLoS) imaging reveals a hidden scene using indirect diffuse reflections. A common choice for analyzing the time-of-flight (ToF) data from a non-confocal system is an ellipsoid model whose operator is high-dimensional, leading to a computationally arduous task. In this Letter, the product-convolution expansions method is utilized to formulate the operator and its adjoint based on the observation of a shift-variant point spread function (PSF) in the ToF data. The operator and its adjoint are locally approximated as a convolution, which allows the forward and backward procedure to be computed efficiently through fast Fourier transform (FFT). Moreover, the low-rank approximation of the operator is obtained by matrix decompositions, further improving the computational efficiency. The proposed method is validated using publicly accessible datasets. © 2022 Optica Publishing Group.
  Accession Number: 20224012831194
• Record 34 of
  
  Title:Fabrication and high temperature characteristics of microtapered long period fiber gratings based on microfibers
  
  Author(s):Wang, Bingchuan(1); Ren, Liyong(2); Kong, Xudong(3); Xu, Yiping(1); Ren, Kaili(3); Yang, Wenxing(1); Cheng, Shubo(1); Li, Yuhui(1); Jiang, Jiabao(1)
  Source: Journal of Optoelectronics and Advanced Materials  Volume: 24  Issue: 11-12  DOI:   Published: November 2022  
  Abstract:Based on the photoelastic effect, a new technology is used to fabricate high quality microtapered long period fiber gratings (MLPFGs) from microfibers. The effects of different periods and number of tapers on the grating spectrum have been explored. The high temperature characteristics of the grating were studied. The results show that MLPFG fabricated from a microfiber has good high temperature stability. With the increase of temperature, the spectrum of grating with a period of 685 μm has the same change trend as that of grating with a period of 670 μm. The temperature sensing sensitivities of gratings with periods of 685 μm and 670 μm are 0.0203 nm°C-1 and 0.01741 nm°C-1, respectively. The critical temperature at which the spectrum of the fabricated MLPFG changes irreversibly is between 600°C and 800°C, which is more than 100°C higher than that reported previously. Another advantage of this type of grating is that it can be used to make torsion sensor. The measurement range is larger than that of grating directly tapered from a single mode fiber (SMF). By observing the shifts of resonant wavelengths, the torsion angle can be determined without taking other measures. © 2022 National Institute of Optoelectronics. All rights reserved.
  Accession Number: 20233414607760
• Record 35 of
  
  Title:Method of compensating for time measurement error of photomultiplier tube
  
  Author(s):Wang, Chong(1); Dang, Wen-Bin(1); Zhu, Bing-Li(2); Yang, Kai(2,3); Yang, Jia-Hao(1); Han, Jiang-Hao(1)
  Source: Wuli Xuebao/Acta Physica Sinica  Volume: 71  Issue: 22  DOI: 10.7498/aps.71.20221193  Published: November 20, 2022  
  Abstract:In order to improve the temporal resolution of photomultiplier tubes, our research group has conducted the in-depth research on photomultiplier tubes based on microchannel plates that are widely used at present. The time resolution of photomultiplier tube based on microchannel plate is limited by the transit time of photoelectric signal in each part, including the transit time of photoelectric signal in the transmission process of photocathode to microchannel plate, the transit time of photoelectric signal in microchannel plate time, the transit time of the photoelectric signal from the microchannel plate to the detector anode, and the transit time of the photoelectric signal on the anode to the electrode port. The transit time of the whole process has a certain degree of influence on the time information measurement of the optoelectronic signal. In this study, various parameters affecting the time resolution of the photomultiplier tube are analyzed, and it is found that the different positions of the photoelectron signal on the anode will bring errors to the measurement of the arrival time of the signal at the anode, and the photoelectric signal is transmitted to the electrode port at the affected point of the anode The spent time will cause the signal measurement time to lag behind the real time, which indirectly affects the time resolution of the system. Therefore, a specific study is carried out on the time measurement error of the signal on the anode, and it is determined that the difference of the photoelectron signal on the anode position is an important factor causing the signal time measurement error, and a simple and effective method of compensating for error is proposed. In the research process, the delay line anode is used, and the positional resolution principle of the photoelectric signal is used to obtain the position information of the photoelectron signal on the anode, and the position information is converted into the time information transmitted from the position to the electrode port. The theoretical value of the transit time on the anode is offset, eliminating unnecessary time in the time-of-arrival measurement of the photoelectron signal. The time measurement error of the optoelectronic signal is compensated for by this time information. The experimental results show that the error compensation method can effectively improve the time measurement accuracy of optoelectronic signals, and provide solutions and theoretical basis for improving the time resolution of photomultiplier tubes based on microchannel plates. © 2022 Chinese Physical Society.
  Accession Number: 20224913216676
• Record 36 of
  
  Title:Rapid full-color Fourier ptychographic microscopy via spatially filtered color transfer
  
  Author(s):Chen, Jiurun(1,2,3); Wang, Aiye(1,2,3); Pan, An(1,2); Zheng, Guoan(4); Ma, Caiwen(1,2); Yao, Baoli(1,2)
  Source: Photonics Research  Volume: 10  Issue: 10  DOI: 10.1364/PRJ.473038  Published: October 1, 2022  
  Abstract:Full-color imaging is of critical importance in digital pathology for analyzing labeled tissue sections. In our previous cover story [Sci. China: Phys., Mech. Astron. 64, 114211 (2021)], a color transfer approach was implemented on Fourier ptychographic microscopy (FPM) for achieving high-throughput full-color whole slide imaging without mechanical scanning. The approach was able to reduce both acquisition and reconstruction time of FPM by three-fold with negligible trade-off on color accuracy. However, the method cannot properly stain samples with two or more dyes due to the lack of spatial constraints in the color transfer process. It also requires a high computation cost in histogram matching of individual patches. Here we report a modified full-color imaging algorithm for FPM, termed color-transfer filtering FPM (CFFPM). In CFFPM, we replace the original histogram matching process with a combination of block processing and trilateral spatial filtering. The former step reduces the search of the solution space for colorization, and the latter introduces spatial constraints that match the low-resolution measurement. We further adopt an iterative process to refine the results. We show that this method can perform accurate and fast color transfer for various specimens, including those with multiple stains. The statistical results of 26 samples show that the average root mean square error is only 1.26% higher than that of the red-green-blue sequential acquisition method. For some cases, CFFPM outperforms the sequential method because of the coherent artifacts introduced by dust particles. The reported CFFPM strategy provides a turnkey solution for digital pathology via computational optical imaging. © 2022 Chinese Laser Press.
  Accession Number: 20230613565944