2020
2020
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Record 277 of
Title:Development of Semiconductor Lasers
Author(s):Chen, Lianghui(1); Yang, Guowen(2,3); Liu, Yuxian(2)Source: Zhongguo Jiguang/Chinese Journal of Lasers Volume: 47 Issue: 5 DOI: 10.3788/CJL202047.0500001 Published: May 10, 2020Abstract:Semiconductor laser has been half a century since its birth, tremendous progress has been made in theory, practice, and applications, and the market occupies more than half of the entire laser field. It is widely used in communication networks, industrial processing, medical and beauty, laser sensing, aviation and defense, security protection, and even consumer electronics. On the basis of reviewing the development history of early domestic and international semiconductor lasers, this article mainly focuses on GaAs-based 8xx nm and 9xx nm semiconductor lasers in the field of high-power pump sources, 905 nm tunnel junction lasers and 940 nm vertical cavity surface emitting lasers in the field of three-dimensional sensing, and GaSb-based infrared lasers and InP-based quantum cascade lasers in the field of spectral analysis and infrared sensing, for a brief review. The content includes the main application scenarios, the main goals pursued, the latest developments in the past 10 years at home and abroad, and the possible development trends and directions in the future. ? 2020, Chinese Lasers Press. All right reserved.Accession Number: 20202908941809 -
Record 278 of
Title:Investigating limiting factors for self-assembly of carbon nanotubes: A molecular dynamics simulation study
Author(s):Zhang, Jianwei(1,3,4); Cui, Jianlei(1,2,3,5); Wei, Fengqi(1,3); Wang, Wenjun(1,4); He, Xiaoqiao(6); Mei, Xuesong(1,4)Source: Applied Surface Science Volume: 504 Issue: DOI: 10.1016/j.apsusc.2019.144397 Published: 28 February 2020Abstract:Multi-scale patterned assembly and integration is an important solution to break through the industrial application of carbon nanotubes (CNTs). The strategy based on self-assembly has yielded fruitful achievements in the practice of fabricating patterns such as two dimensional arrays. However, the mechanism of self-assembly of CNTs and the key factors that limit the fidelity of patterns have always been an unresolved issue. In this paper, all-atomic molecular models for studying the mechanism of hydrophilic/hydrophobic self-assembly are established and some key factors limiting the fidelity of SWNTs patterns are thoroughly investigated. The results show that chiral indices have little effect on the results of self-assembly. Secondly, edge effect determines the assembly sequence on hydrophilic surface and self-assembly will not occur when M-SWNTs are above the hydrophilic/hydrophobic interface. Thirdly, the assembly sequence of M-SWNTs in different layers of the solution is dominated by the competition of H2O molecules. At last, shielding effect is very important for the study of how to improve the density of SWNTs in the pattern. The explicitly results are not only helpful to understand many phenomena in self-assembly process at the atomic scale but also will provide meaningful guidance in fabrication of SWNTs patterns to prevent distortion. ? 2019 Elsevier B.V.Accession Number: 20194807742221 -
Record 279 of
Title:Study on fabrication, spectrum and torsion sensing characteristics of microtapered long-period fiber gratings
Author(s):Wang, Bingchuan(1); Ren, Liyong(2); Kong, Xudong(3); Xu, Yiping(1); Ren, Kaili(3); Yang, Wenxing(1); Cheng, Shubo(1); Chen, Fang(1); Song, Feng(1,4)Source: Optik Volume: 207 Issue: DOI: 10.1016/j.ijleo.2020.164445 Published: April 2020Abstract:Based on the photoelastic effect, a microtapered long-period fiber grating (MLPFG) is fabricated by using a CO2 fusion splicer, which has high repeatability and small loss. By analyzing the spectrum of the grating, it is easy to know that the grating has a significant absorption effect only for light with a specific wavelength (such as λ≈1569 nm). In the process of fabrication, it is found that with the increase of refractive index modulation, the extinction ratio of the spectrum increases gradually, and the resonant dip drifts toward the long wavelength. In addition, it is found that the twist direction and the torsion angle of the grating can be judged by observing the change of the spectrum in the experiment of exploring the sensing of torsion. When the grating is twisted clockwise, wavelength and extinction ratio of the resonant dip decrease gradually; when the grating is twisted counterclockwise, the wavelength increases gradually, but the extinction ratio increases first and then decreases. The torsion sensitivity is 0.10 nm · mm · rad?1, which is about two times higher than that of CLPGs fabricated from photonic crystal fibers and about three times higher than that of conventional LPFGs. By utilizing these characteristics of MLPFG, it can be widely used in filters and sensors. ? 2020 Elsevier GmbHAccession Number: 20200808207332 -
Record 280 of
Title:Chromatic dispersion characterization for meter-long CMOS compatible spiral waveguides
Author(s):Zeng, Lanqian(1); Wang, Linghua(1); Li, Yuhua(2); Chu, Sai T.(2); Little, Brent E.(3); Wang, Shao Hao(1)Source: 2020 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2020 - Proceedings Volume: Issue: DOI: 10.1364/CLEOPR.2020.C11H_5 Published: August 2020Abstract:We demonstrated that the chromatic dispersion of CMOS-compatible waveguide sets increases with their thickness from -465 to 45 ps/nm/km by extending the measuring range of interferometer-based scheme beyond the maximum length of optical delay line. ? 2020 IEEE.Accession Number: 20205209687992 -
Record 281 of
Title:A Highly Cost-Efficient Large-Scale Uniform Laminar Plasma Jet Array Enhanced by V–I Characteristic Modulation in a Non-Self-Sustained Atmospheric Discharge
Author(s):Li, Jing(1,2,3); Wang, Jing(1,2); Lei, Bingying(1,2); Zhang, Tongyi(1,2); Tang, Jie(1,2); Wang, Yishan(1,2); Zhao, Wei(1,2); Duan, Yixiang(1,2,4)Source: Advanced Science Volume: 7 Issue: 6 DOI: 10.1002/advs.201902616 Published: March 1, 2020Abstract:Developing cost-efficient large-scale uniform plasma jets represents a significant challenge for high performance in material processing and plasma medicine. Here, a V–I characteristic modulation approach is proposed to reduce the discharge power and increase the plasma scale and chemical activity in non-self-sustained atmospheric direct-current discharges. The electric field in discharge space is optimized to fundamentally empower simultaneously initiating all discharge cells far below Townsend breakdown potential and stably sustaining each plasma jet at low voltage. These strategies create a crucial step to fabricating a flexible and compact low-power large-scale uniform laminar plasma jet array (LPJA) with high activity in cheap argon. The mechanisms behind the discharge enhancement are revealed by combining V–I characteristic examination and a modulation model. Compared with conventional arrays, this LPJA possesses the widest size (90 mm) and raises its uniformity from 30% to 97%. Comparing different discharge modes shows that the LPJA scale is surprisingly increased nearly by 4 times with the discharge power reduced from 7.4 to 4.8 W. The methodology provides a highly cost-efficient roadmap to break through the bottleneck of restricting low-power discharge, large-gap discharge, large-scale discharge, parallel-multi-electrode discharge, and uniform discharge together. This advance will meet the urgent need for various plasma applications. ? 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimAccession Number: 20200408064554 -
Record 282 of
Title:Ultrahigh-precision measurement timing jitter based on self-reference source
Author(s):Xu, Peng(1,2); Liu, Yuan-Shan(3); Zhang, Jian-Guo(1,4)Source: Guangxue Jingmi Gongcheng/Optics and Precision Engineering Volume: 28 Issue: 11 DOI: 10.37188/OPE.20202811.2429 Published: November 2020Abstract:Timing jitter is a key parameter of low-noise systems, including optical frequency combs and low-noise laser microwave photon radar systems. Consequently, precisely measuring its values is quite important. The traditional direct detection method is limited by the floor noise of the microwave oscillator or photodetector noise, and its measurement accuracy is relatively low. Optical measuring methods, such as optical heterodyne and optical cross-correlation methods, are very complicated and have relatively high requirements on both reference and measured sources. This study presents a method to measure timing jitter with high precision without using a reference source, thereby overcoming some deficiencies of traditional methods. Based on long fiber delay line technology and optical carrier frequency interference, an attempt is made to realize ultra-high precision for measuring timing jitter. Results from the simulated system show that the noise base of a 10-MHz laser is 3.29 × 10-13 fs2/Hz (equivalent to -211 dBc/Hz) when the frequency deviation is 100 MHz at its 100th power harmonic point 10 GHz, and the total root mean square timing jitter from 10 kHz to 10 MHz is 535 as, which has an obvious advantage for ultra-low timing jitter measurement. This measurement method is a convenient, high-efficiency method that can be applied to different measured sources, such as passively mode-locked lasers, optical frequency combs, and super-continuum spectra. ? 2020, Science Press. All right reserved.Accession Number: 20205209688721 -
Record 283 of
Title:Research on CNN Denoising Algorithm Based on an Improved Mathematical Model for the Measurement of Far-field Focal Spot
Author(s):Wang, Zheng-Zhou(1); Wang, Li(1); Tan, Meng(1); Duan, Ya-Xuan(1); Wang, Wei(1); Tian, Xin-Feng(1); Wei, Ji-Tong(1)Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 49 Issue: 12 DOI: 10.3788/gzxb20204912.1212001 Published: December 2020Abstract:Aim at the shortcomings that the mathematical model for the measurement of far-field focal spot with high dynamic range does not consider the influence of noise on the measurement results, this paper optimizes the measurement method of far-field focal spot based on schlieren from three aspects. Firstly, the mathematical model for the measurement of far-field focal spot based on schlieren is improved, and the noise is added to the mathematical model, which makes the mathematical model match with the real experimental environment, and improves the practicability and theoretical support of the mathematical model; Secondly, the denoising algorithm based on Convolution Neural Network (DnCNN) is used in the de-noise processing of the main lobe and side lobe CCD image, and the original denoising algorithm is improved effectively in this paper, which can remove the noise of different levels (0~75 dB) of the mainlobe and sidelobe 12-bit images; Finally, the whole experimental process of far-field focal spot measurement is simulated, including light splitting, attenuation, adding noise, schlieren sphere occlusion, denoising, attenuation magnification, focal spot reconstruction, etc., and the effective experimental results of reconstructed focal spot is obtained, which the correlation coefficient between the reconstructed and theoretical focal spot images is 0.998 9, and the error of dynamic range between the reconstructed and theoretical focal spot is 3.22%. The simulation results show that through the improvement of the mathematical model and the DnCNN denoising algorithm, the necessity of the improved mathematical model and the superior performance of the DnCNN denoising algorithm in improving the accuracy of the two-dimensional distribution and dynamic range of reconstructed focal spot are verified. The reliability of the measurement of far-field focal spot with high dynamic range based on schlieren is improved, and the accuracy and efficiency of the measurement of far-field focal spot in high dynamic range is met in the end. ? 2020, Science Press. All right reserved.Accession Number: 20210209739053 -
Record 284 of
Title:UAV target saliency detection based on frequency domain transform
Author(s):Wang, Xin(1); Li, Zhe(1); Tian, Yan(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 11567 Issue: DOI: 10.1117/12.2576594 Published: 2020Abstract:In order to solve the difficult problem of unmanned air vehicle(UAV) target detection in visible light images under complex sky background, this paper proposes a UAV target detection method based on frequency domain transform. First, the B-channel in the image LAB space is used to extract the sky and cloud boundary images, and then the image feature channel is used to construct a quaternion function. Secondly, Fourier transform is performed on the quaternion function to extract the amplitude spectrum and phase spectrum, then the amplitude spectrum image is subjected to multi-scale decomposition using wavelet transform in the frequency domain, the amplitude spectrum image of each scale and the phase spectrum image are combined by inverse Fourier transform, and the evaluation function is used to obtain the best scale image. Finally, the best-scale image and the boundary image are normalized to make a difference to obtain the final detection result. Experimental results show that the algorithm can effectively detect UAV targets under complex cloud background. ? 2020 SPIE.Accession Number: 20205009602570 -
Record 285 of
Title:Optically Multiplexed Imaging for Increased Field of View
Author(s):Zhou, Liang(1); Liu, Kai(1); Liu, Zhao-Hui(1); Duan, Jing(1); Li, Zhi-Guo(1)Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 49 Issue: 9 DOI: 10.3788/gzxb20204909.0911001 Published: September 1, 2020Abstract:In order to simplify the multiplexing architecture and encoding method, a two-channels multiplexed imaging architecture was constructed with rotation encoding mirror, beamsplitter and optically imaging system. The subpixel accuracy shifts between superimposed images were proposed to automatically decide with features detection and registration. The system multiplexed matrics were built with the known shifts and the gradient projection for sparse reconstruction method was adopted to reconstruction the respctive scene based on six frames. The increase of field of view was verified with 2 times in the proposed realistic setting. Also, the proposed method can sucessfully disambiguate other scenes, which demonstrates its wide range of application. This method can effectively increase the field of view with the same focal plane array, and can be cost effective in developing wide field of view optically imaging system. ? 2020, Science Press. All right reserved.Accession Number: 20203909225437 -
Record 286 of
Title:Image Motion Measurements Based on Intensity Superimposition and Joint Transform Correlation Approach
Author(s):Yi, Hongwei(1); Li, Xuyang(1); He, Tianbing(1); Chen, Rongli(1)Source: Zhongguo Jiguang/Chinese Journal of Lasers Volume: 47 Issue: 3 DOI: 10.3788/CJL202047.0304003 Published: March 10, 2020Abstract:To achieve high speed, high precision, and device miniaturization, an improved joint transform correlation (JTC) method is proposed. In this method, the correlation input image is constructed by superposing the intensity of two images to be detected. To effectively separate autocorrelation and cross correlation peaks, the method makes use of the constant image motions resulting from satellite movement. The size of each image used for the correlation operation is reduced to the size of the image to be detected, which greatly reduces the calculation of the measurement process, which is beneficial for realizing high-speed digital joint transform correlation. The simulated and experimental results show that the new method maintains the advantages of high accuracy, high robustness to image noise and low dependency on image texture of traditional JTC. Additionally, it also has the potential for high-speed image motion measurements. ? 2020, Chinese Lasers Press. All right reserved.Accession Number: 20202308791571 -
Record 287 of
Title:Dynamic surface parameter analysis for frequency response of tip/tilt mirror
Author(s):Xu, Guangzhou(1)Source: Optik Volume: 203 Issue: DOI: 10.1016/j.ijleo.2019.163964 Published: February 2020Abstract:The tip/tilt mirror performs controllable high-speed swing to stabilize the imaging beam and compensate for the external micro-vibration for optical telescope. The calculation of surface parameter under dynamic driven frequency is the design foundation of tip/tilt mirror. To resolve the dynamic surface parameter calculation problem, the frequency response analysis of tip/tilt mirror is carried out; the discrete error and elimination method of optical surface for tip/tilt mirror is proposed as well to improve the surface calculation precision of tip/tilt mirror; the opto-mechanical simulation technology is selected to process the dynamic surface change data of tip/tilt mirror and it has been proved the effectiveness to obtain the dynamic surface parameter of tip/tilt mirror. The calculation results demonstrate the nonlinear change rule between the surface change parameter and the driven frequency; the surface change is not obvious under the lower micro-vibration driven frequency, but is obvious under the higher driven frequency; the micro-vibration frequency and environmental adaption of tip/tilt mirror are determined based on the dynamic surface parameter simulation results. The research of dynamic surface parameter for frequency response of tip/tilt mirror provides a new technical reference for the dynamic surface simulation and structural design of tip/tilt mirror. ? 2019 Elsevier GmbHAccession Number: 20195107869965 -
Record 288 of
Title:Development of a 67.8 W, 2.5 ps ultrafast chirped-pulse amplification system based on single-crystal fiber amplifiers
Author(s):Wang, Na Na(1,2); Li, Feng(1); Wang, Xiang Lin(1); Hu, Xiao Hong(1); Wang, Yi Shan(1); Zhao, Wei(1)Source: Applied Optics Volume: 59 Issue: 27 DOI: 10.1364/AO.399680 Published: September 2020Abstract:We demonstrate a high-power, high-energy chirped-pulse amplification (CPA) system based on three Yb:YAG amplifiers and a chirped-volume Bragg grating (CVBG). With an all-fiber laser as the seed light, a Yb:YAG rod amplifier and two Yb:YAGsingle-crystal fiber (SCF) amplifiers as the amplification stages, a laser power of 96Wat 200 kHz repetition rate corresponding to a pulse energy of 0.48 mJ has been generated. The stability of different output power has been measured and compared. To the best of our knowledge, this is the first report on a stable 100W-level laser with sub-mJ pulse energy based on SCF. The beam quality M2 of different output lasers has also been measured, which is below 1.55 when the output power is 92W. The amplified laser is seeded into the CVBG to be compressed, and a compression efficiency of 0.724 has been obtained with an output power of 67.8Wand pulse duration of 2.5 ps. The ultrafast CPA system delivering high pulse energy (sub-mJ) with hundreds of kHz repetition rate is expected to be used as the driving source of high-flux high-harmonic generation after further compression. ?2020 Optical Society of America.Accession Number: 20204009302719