2023

• Record 205 of
  
  Title:Broadband polarization-independent achromatic varifocal metalens in the terahertz region
  
  Author(s):Wu, Qi(1,2); Fan, Wen-Hui(1,2,3); Qin, Chong(1,2); Jiang, Xiao-Qiang(1,2)
  Source: Journal of the Optical Society of America B: Optical Physics  Volume: 40  Issue: 6  Article Number: null  DOI: 10.1364/JOSAB.488592  Published: June 2023  
  Abstract:Lenses with tunable focal lengths are quite critical to various optical sensors, imaging, and detection systems. A traditional varifocal system is usually composed of multiple conventional refractors and needs to mechanically adjust the axial distance among them, inevitably leading to complex operation and bulky volume. Recently, metasurfaces have provided an alternative for flexibly shaping the electromagnetic field. However, simultaneously realizing continuous zoom and achromatic function remains a challenge. This paper proposes an achromatic continuous varifocal metalens consisting of two coaxial metasurfaces working in the terahertz range. The underlying mechanism depending on the superimposed phase distribution of these two metasurfaces is similar to a spherical lens, and the focal length can be continuously varied by changing the mutual rotation angle. The tuning range of focal length is continuous from 3.08 mm to 11.52 mm, corresponding to the numerical aperture from 0.58 to 0.19. Meanwhile, careful dispersion engineering based on the particle swarm optimization algorithm has also achieved achromatic bandwidth ranging from 0.9 THz to 1.2 THz. The maximum deviation of the focus length is below 8%, and the coefficient variations of the focal lengths among the entire bandwidth are under the allowed scope (5%) of the international standard of chromatic aberration, while a focusing efficiency of 32% can be obtained simultaneously. This scheme will provide promising opportunities and possibilities for future display technology and integrated optical imaging systems. © 2023 Optica Publishing Group.
  Accession Number: 20232714340884
• Record 206 of
  
  Title:Propagation characteristic of OAM blue-green laser in seawater
  
  Author(s):Jing, Li(1); Feng, Wang(2); Rong, Lu(3)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12921  Issue: null  Article Number: 1292146  DOI: 10.1117/12.2691752  Published: 2023  
  Abstract:The blue-green laser, which is attenuated less in water, are of potential applications in the deep seawater communication. The orbital angular momentum (OAM) as a new degree of freedom with characteristic of unlimited topological charge, is expected to extensive improve the capacity of blue-green laser communication. In seawater channel, the turbulence is the main factor to influence laser transmission, thus, it is important to research the effect of seawater turbulence on OAM blue-green laser. In this paper, base on power spectrum method the phase screen effected by turbulence is studied, and the transmission model for OAM LG laser in the presence of seawater turbulence is established. For typical wavelength of 532nm, the received laser power and phase is analyzed with different transmitted distance and beam waist.Mathematical simulation shows that, the smaller the beam waist is, the better the OAM spiral phase matains and the stronger the received laser power is, since the turbulence influence is less, which means the smaller beam waist obtains obvious advantages. The results can benefit the transmission characteristic analysis and modulation for underwater blue-green laser channel research, and provide foundation for system optimum design. © 2023 SPIE.
  Accession Number: 20234815132623
• Record 207 of
  
  Title:Simulation and an experimental study on the optical performance of a Wolter-I focusing mirror based on a 3D ray tracing algorithm
  
  Author(s):Wu, Kaiji(1); Ding, Fei(1); Wang, Bo(1); Yang, Yanji(2); Wang, Yusa(2); Qiao, Zheng(1); Li, Duo(1); Jin, Yuan(1); Qiang, Pengfei(3); Zhao, Zijian(2); Hou, Dongjie(2); Zhu, Yuxuan(2)
  Source: Optics Express  Volume: 31  Issue: 19  Article Number: null  DOI: 10.1364/OE.497987  Published: September 11, 2023  
  Abstract:The nestedWolter-I type focusing mirror is widely used in the field ofX-ray astronomy. The thin-shell mirrors produced by the electroforming replication method will introduce various shape errors during the fabricating and assembling process. This study introduces a non-analytical 3D geometrical ray tracing algorithm capable of predicting optical performance for large mirror deformations. The algorithm's implementation involves error reconstruction, light source and ray simulation, and optical performance calculation. Experimental and simulation validation underscores the algorithm's precision and effectiveness. The results also indicate that edge deformation can seriously affect imaging contrast which is generally considered to be determined only by surface scattering. Applying the 3D ray tracing algorithm, a range of low-frequency fabrication and assembly errors are simulated, such as absolute radius, taper, roundness, edge effects, mirror posture, and hoisting deformation errors, and their effects on imaging quality are analyzed and discussed. © 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
  Accession Number: 20241015699461
• Record 208 of
  
  Title:Phase control scheme of the coherent beam combining system for generating perfect vectorial vortex beams assisted by a Dammann vortex grating
  
  Author(s):Ju, Pei(1,2); Fan, Wenhui(1,2,3); Gao, Wei(1,2); Li, Zhe(1,2); Gao, Qi(1,2); Jiang, Xiaoqiang(1,2); Zhang, Tongyi(1,2)
  Source: Optics Express  Volume: 31  Issue: 14  Article Number: null  DOI: 10.1364/OE.493649  Published: July 3, 2023  
  Abstract:Based on Dammann vortex grating and adaptive gain stochastic parallel gradient descent algorithm, we theoretically proposed a phase control technology scheme of the coherent beam combining system for generating perfect vectorial vortex beams (VVBs). The simulated results demonstrate that the discrete phase locking for different types of VVBs (including vortex beams, vector beams, and generalized VVBs) can be successfully realized. The intensity distributions, polarization orientation, Pancharatnam phases, and beam widths of different |Hm,n states with the obtained discrete phase distribution further prove that the generated beams are perfect VVBs. Subsequently, the phase aberration residual for different VVBs is evaluated using the normalized phase cosine distance function, and their values range from 0.01 to 0.08, which indicates the obtained discrete phase distribution is close to the ideal phase distribution. In addition, benefitting from the high bandwidth of involved devices in the proposed scheme, the influence of dynamic phase noise can be negligible. The proposed method could be beneficial to realize and switch flexible perfect VVBs in further applications. © 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
  Accession Number: 20232914397494
• Record 209 of
  
  Title:Athermalization of Optical System with Large Field of View for Image Navigation
  
  Author(s):Zhang, Jialei(1,2); Xue, Yaoke(1,2,3,4,5); Zhou, Canglong(1); Lin, Shangmin(1,2); Liu, Meiying(1,2)
  Source: Journal of Physics: Conference Series  Volume: 2617  Issue: 1  Article Number: 012007  DOI: 10.1088/1742-6596/2617/1/012007  Published: 2023  
  Abstract:Image navigation sensor is one of the most important sensing means for human to explore the extraterrestrial space environment, and optical system is a key component of image navigation sensor, directly determines the amount of information perceived. The optical system requirements of image navigation sensors are gradually developing towards large field of view and miniaturization. The fisheye lens is the first choice for large field of view imaging by selecting the appropriate optical structure, without adding other additional components, and has the advantages of small size and strong perception energy. However, as the image surface illuminance of fisheye lens will decrease sharply with the increase of the field of view, the change of temperature will also degrade the imaging quality of the system, and strong stray light sources such as the sun will easily enter the field of view, which will greatly affect the perception ability of the system. Because of this, effective design of these systems is quite difficult. In this paper, a reverse-telephoto structure was used for large-field imaging, and the degradation of imaging quality caused by temperature changes was eliminated by selecting appropriate optical and mechanical materials. Designed with a focal length of 6.7mm, an F number of 3.6, a viewing angle of 130°, a working band of 0.45μm to 0.65μm, an after work distance of 7mm, a total system length≤60mm, we tested our system in a -40°C to +60°C temperature range and measured the image quality. Through simulation analysis, the system in the whole field of view within our spot diagrams was≤5.5μm, optical transfer function was greater than 0.2 at 90lp/mm, and no vignetting occurred. Furthermore, the imaging illumination of the edge field of view was 0.72 times that of the center field of view, the f - tan (θ) relative distortion value of the center field of view was≤2.3%, and the f - θ relative distortion value of the edge field of view was≤2.7%. Compared to normal temperatures, the optical transfer function changes at -20°C and +40°C were 0.02 and 0.01, respectively. Thus, the system displayed the characteristics of excellent image quality, small size, high energy utilization rate and good non-thermal performance. © Published under licence by IOP Publishing Ltd.
  Accession Number: 20234615063752
• Record 210 of
  
  Title:Enhanced terahertz wave generation in air-plasma induced by femtosecond three-color harmonic pulses
  
  Author(s):Wang, Han-Qi(1,2); Fan, Wen-Hui(1,2,3); Chen, Xu(1); Yan, Hui(1,2)
  Source: Hongwai Yu Haomibo Xuebao/Journal of Infrared and Millimeter Waves  Volume: 42  Issue: 6  Article Number: null  DOI: 10.11972/j.issn.1001-9014.2023.06.011  Published: 2023  
  Abstract:The generation of terahertz waves from air-plasma induced by femtosecond three-color harmonic pulses with a frequency ratio of 1:2:m（m is a positive integer),based on the transient photocurrent model and the sawtooth-like electric field formed via multi-color harmonic pulses superposition,has been theoretically investigated. It can be seen that when the air is saturated ionized and the electron density reaches the same maximum,for the same number of harmonic pulses,terahertz conversion efficiency is not always higher when the electric field shape in the composed pulse envelope is closer to a sawtooth waveform and more asymmetric. Besides,the specific wavelength combination schemes of femtosecond three-color harmonic pulses with the frequency ratios of 1: 2:3 and 1:2:4 have also been simulated,which can significantly enhance the generation of terahertz waves,and are realized by adding only a set of optical parametric amplifiers on the basis of the conventional two-color laser pulse case at the frequency ratio of 1:2. Our study will be helpful to obtain intense terahertz sources and provide guidance for experimental operations. © 2023 Chinese Optical Society. All rights reserved.
  Accession Number: 20234915148412
• Record 211 of
  
  Title:Polarization control of terahertz waves generated by a femtosecond three-color pulse scheme
  
  Author(s):Wang, Hanqi(1,2); Fan, Wenhui(1,2,3); Chen, Xu(1); Yan, Hui(1,2)
  Source: Journal of the Optical Society of America B: Optical Physics  Volume: 40  Issue: 6  Article Number: null  DOI: 10.1364/JOSAB.484521  Published: June 2023  
  Abstract:Polarization characteristics of terahertz waves generated from a short air plasma excited by femtosecond three-color pulses with a frequency ratio of 1:2:3 have been theoretically investigated, and the results show that flexible and effective control of terahertz polarization can be achieved by means of changing the polarization combination and relative phase of three-color pulses, which is related to the electric field spatiotemporal distribution of the synthetic pulse formed via three-color pulse superposition. The complicated spatiotemporal distribution can be made clear by analyzing the projection component of the electric field in the three-dimensional Cartesian coordinate system. For terahertz waves generated from a short air plasma filament, the proposed method of terahertz polarization control on the basis of a three-color pulse scheme can be realized by ordinary multi-cycle laser pulses and overcome the disadvantage of few-cycle laser pulses utilized to obtain nearly circularly polarized intense terahertz waves or elliptically polarized intense terahertz waves with large ellipticity in the two-color pulse scheme. © 2023 Optica Publishing Group.
  Accession Number: 20232214155305
• Record 212 of
  
  Title:Multi-foci metalens based on all-dielectric metasurface with simultaneous amplitude and phase modulation
  
  Author(s):Qin, Chong(1,2); Fan, Wenhui(1,2,3); Wu, Qi(1,2); Jiang, Xiaoqiang(1,2); Yan, Hui(1,2)
  Source: Journal of Optics (United Kingdom)  Volume: 25  Issue: 11  Article Number: 115103  DOI: 10.1088/2040-8986/acf054  Published: November 1, 2023  
  Abstract:Metasurfaces provide a novel platform for designing high efficiency and multi-functional photonic devices with compact size. Multi-foci metalens have great potential in the applications of optical tomography technology, optical data storage, optical communication and photoelectric detection. Here, in order to broaden the functionality and applicability of multi-foci metalens, a scheme for designing multi-foci metalens based on all-dielectric metasurface with simultaneous amplitude and phase modulation is demonstrated. Based on this, a linear-polarization-dependent multi-foci metalens which can focus x-polarization and y-polarization incident wave into multiple focal points independently is designed and demonstrated numerically, the intensity ratio between the x-polarization foci and y-polarization foci can be tuned continuously by varying the polarization angle of incident wave. In addition, the polarization-independent multi-foci metalens and dual-frequency multi-foci metalens have also been demonstrated by utilizing this method, the intensity ratio among these foci can be designed at will. This work is of great significance for the practical applications of multi-foci metalens. © 2023 IOP Publishing Ltd.
  Accession Number: 20234515007553
• Record 213 of
  
  Title:Generation of perfect vectorial vortex beams by employing coherent beam combining
  
  Author(s):Ju, Pei(1,2); Fan, Wenhui(1,2,3); Gao, Wei(1,2); Li, Zhe(1,2); Gao, Qi(1,2); Li, Gang(1,2); Jiang, Xiaoqiang(1,2); Zhang, Tongyi(1,2)
  Source: Optics Express  Volume: 31  Issue: 7  Article Number: null  DOI: 10.1364/OE.485396  Published: March 27, 2023  
  Abstract:Based on coherent beam combining, we propose a method for generating the perfect vectorial vortex beams (VVBs) with a specially designed radial phase-locked Gaussian laser array, which is composed of two discrete vortex arrays with right-handed (RH) and left-handed (LH) circularly polarized states and in turn adjacent to each other. The simulation results demonstrate that the VVBs with correct polarization order and topological Pancharatnam charge are successfully generated. The diameter and thickness of generated VVBs independent of the polarization orders and topological Pancharatnam charges further prove that the generated VVBs are perfect. Propagating in free space, the generated perfect VVBs can be stable for a certain distance, even with half-integer orbital angular momentum. In addition, constant phases φ0 between the RH and LH circularly polarized laser arrays has no effect on polarization order and topological Pancharatnam charge but makes polarization orientation to rotate φ0/2. Moreover, perfect VVBs with elliptically polarized states can be flexibly generated only by adjusting the intensity ratio between the RH and LH circularly polarized laser array, and such perfect VVBs are also stable on beam propagation. The proposed method could provide a valuable guidance for high power perfect VVBs in future applications. © 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
  Accession Number: 20231714021605
• Record 214 of
  
  Title:Study on Acoustic Characteristics of Environmental Noise in Low Pressure Enclosed Spaces
  
  Author(s):Li, Biao(1); Zhang, Haifeng(2); Qiao, Tiezhu(3); Li, Jingxia(4); Fang, Yao(2)
  Source: 2023 IEEE 6th International Conference on Information Systems and Computer Aided Education, ICISCAE 2023  Volume: null  Issue: null  Article Number: null  DOI: 10.1109/ICISCAE59047.2023.10393354  Published: 2023  
  Abstract:In order to study the impact of low pressure environment on acoustic measurement, different pressure environments were simulated in a low pressure experimental chamber to conduct measurement research on environmental noise under low pressure environment. The measurement equipment used DS-2MC1001-W microphone, and the sound source output was environmental noise. The pressure inside the test chamber was reduced from 101kPa to 1kPa, and a set of data was measured every 10kpa. The acoustic characteristics of the measured data were recorded, including pitch frequency, sound pressure level Analyze the acoustic data of environmental noise at different pressure levels from the perspective of A-weighted sound pressure level and 1/3 octave A-weighted sound pressure level, and explore the attenuation of environmental noise at different pressure levels and the main frequency bands of noise. The research results indicate that as the air pressure decreases, all of the above parameters decay. When the air pressure drops to 1kPa, the sound pressure level decreases by 8.31dB, and the A-weighted sound level decreases by 8.41dBA. Among them, the sound source noise is mainly in the frequency range of 0-4000Hz. © 2023 IEEE.
  Accession Number: 20240815573904
• Record 215 of
  
  Title:Research on the algorithm of 3D pose solving based on binocular vision
  
  Author(s):Wu, Jiaxin(1,2); Ai, Han(1,2); Zhang, Hai Feng(1,3); Cao, Jianzhong(1,3)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12704  Issue: null  Article Number: 127043C-1  DOI: 10.1117/12.2680583  Published: 2023  
  Abstract:Due to the complex lighting environment in space, the surface coating material of the spacecraft is uneven and has strong reflection characteristics, resulting in the complex problem of extremely bright or extremely dark in the image under sunlight, and it is difficult to extract stable features. In addition, for the actual measurement system, the amount of data for image feature processing and image matching is large, which makes the speed of the key algorithm unable to meet the real-time nature of the application. Therefore, based on the above problems, this paper proposes a set of three-dimensional measurement algorithms based on binocular vision, mainly has four parts, camera calibration, Image correction, stereo matching and pose solving. We use traditional image processing algorithm for satellite image, using M software for camera calibration, and the calibration results are further optimized and corrected, due to the requirements of real-time, based on ORB algorithm, the use of Fast algorithm for feature point extraction and descriptor calculation by Brief, and the polar constraint is fused for feature matching. Improve the robustness and real-time performance of the algorithm, and perform pose solving by rotating angle. Experiments show that the algorithm can quickly and accurately achieve three-dimensional pose measurement. © 2023 SPIE. All rights reserved.
  Accession Number: 20234114870463
• Record 216 of
  
  Title:Multiple Source Domain Adaptation for Multiple Object Tracking in Satellite Video
  
  Author(s):Zheng, Xiangtao(1); Cui, Haowen(2,3); Lu, Xiaoqiang(1)
  Source: IEEE Transactions on Geoscience and Remote Sensing  Volume: 61  Issue: null  Article Number: 5626911  DOI: 10.1109/TGRS.2023.3336665  Published: 2023  
  Abstract:Satellite videos capture the dynamic changes in a large observed sense, which provides an opportunity to track the object trajectories. However, existing multiple object tracking (MOT) methods require massive video annotations, which is time-consuming and fallible. To alleviate this problem, this article proposes a cross-domain multiple object tracker (CDTrack) to learn knowledge from multiple source domains. First, a cross-domain object detector with multilevel domain alignment is constructed to learn domain-invariant knowledge between remote sensing images and satellite videos. Second, the proposed method adopts a bidirectional teacher-student framework to fuse multiple source domains. Two teacher-student models learn different domain knowledge and teach mutually each other. With mutual learning, the proposed method alleviates the discrepancies between different domains. Finally, a simple weakly supervised Re-IDentification (Re-ID) model is proposed for long-term association. Experimental results on the satellite video datasets demonstrate that the proposed method can achieve great performance without satellite video annotations. The code is available at https://github.com/XiangtaoZheng/CDTrack. © 1980-2012 IEEE.
  Accession Number: 20234915181718