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Record 277 of
Title:Low loss and polarization-insensitive coupling length for a terahertz fiber directional coupler with symmetric dual-suspended core structure
Author(s):Zhu, Yuan-Feng(1,2,3); Huang, Xu(1); Ke, Qiang(1); Liu, Guiqiang(1); Rao, Chun-Fang(1); Kong, Depeng(4); Mei, Sen(4); Liu, Yunqi(2); Wang, Hua(5)
Source: Optics Communications Volume: 480 Issue: DOI: 10.1016/j.optcom.2020.126497 Published: February 1, 2021
Abstract:In this work, a terahertz (THz) fiber directional coupler with a symmetric dual-suspended core structure has been proposed for realizing low loss and polarization-insensitive coupling length in the THz frequency region. The fiber core of the directional coupler consists of two round solid dielectric rods supported by two intersecting thin dielectric layers. Numerical simulations performed using the full-vector finite element method show that a short polarization-independent coupling length can be obtained by adjusting the geometric parameters of the fiber. Moreover, a low-loss THz fiber directional coupling performance can also be achieved at a central frequency of 1.00-THz and approximately 0.16 THz of bandwidth. For example, a coupler with a length of 0.421 cm has a transmission loss of 0.30 dB and 0.26 dB for the x- and y-polarization modes, respectively. ? 2020
Accession Number: 20204109338340
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Record 278 of
Title:Genetic Deep Learning for Photonic Device Inverse Design
Author(s):Ren, Yangming(1); Zhang, Lingxuan(1); Zhang, Wenfu(1); Sun, Xiaochen(1)
Source: 2021 IEEE Photonics Conference, IPC 2021 - Proceedings Volume: Issue: DOI: 10.1109/IPC48725.2021.9593021 Published: 2021
Abstract:We demonstrate an inverse design method by combining deep neural networks and genetic optimization. The method significantly reduces the training data compared with existing methods. The method is adopted to design some ultra-compact photonic devices to show its high computing efficiency and great flexibility. ? 2021 IEEE.
Accession Number: 20220411504435
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Record 279 of
Title:Aperture-averaged scintillation index and fade statistics in weak oceanic turbulence
Author(s):Wang, Hao(1,2); Kang, Fu-Zeng(1); Wang, Xuan(3,4); Zhao, Wei(1); Sun, Shu-Wei(1,2)
Source: Chinese Physics B Volume: 30 Issue: 6 DOI: 10.1088/1674-1056/abd756 Published: May 2021
Abstract:With the rapid demand for underwater optical communication (UOC), studies of UOC degradation by oceanic turbulence have attached increasing attention worldwide and become a research hot-spot in recent years. Previous studies used a simplified and inaccurate oceanic turbulence spectrum, in which the eddy diffusivity ratio between temperature and salinity is assumed to be unity and the outer scale of turbulence is assumed to be infinite. However, both assumptions are not true in most of the actual marine environments. In this paper, based on the Rytov theory in weak turbulence, we derive analytical expressions of "the aperture-averaged scintillation index"(SI) for both plane and spherical waves, which can clearly demonstrate how SI is influenced by several key factors in UOC. Then, typical fade statistics of the UOC system in weak turbulence is discussed including the probability of fade, the expected number of fades per time, the mean fade time, signal-to-noise ratio and bit error rate. Our results show that spherical wave is preferable in the UOC system in weak turbulence compared to plane wave, and the aperture-averaged effect has a significant impact on UOC system's performance. Our results can be used to determine those key parameters for designing the UOC system over reasonable ranges. ? 2021 Chinese Physical Society and IOP Publishing Ltd.
Accession Number: 20212510520186
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Record 280 of
Title:Lidar-radar for underwater target detection using a modulated sub-nanosecond Q-switched laser
Author(s):Li, Guangying(1,2); Zhou, Qiang(3); Xu, Guoquan(4); Wang, Xing(1); Han, Wenjie(5); Wang, Jiang(3); Zhang, Guodong(3); Zhang, Yifan(4); Yuan, Zhi'an(4); Song, Sijia(5); Gu, Shangtai(4); Chen, Fubin(4); Xu, Ke(4); Tian, Jinshou(1); Wan, Jianwei(4); Xie, Xiaoping(1,2); Cheng, Guanghua(3)
Source: Optics and Laser Technology Volume: 142 Issue: DOI: 10.1016/j.optlastec.2021.107234 Published: October 2021
Abstract:Here we report on a modulated sub-nanosecond lidar-radar for underwater target detection. The modulated laser source is consisted of a 1064 nm master oscillator power amplifier (MOPA) and a frequency-doubling module, outputting pulse energy of 178.1 mJ at 1064 nm with 0.76 ns pulse duration and 87.6 mJ at 532 nm. By using a Fabry–Pérot cavity containing a KTP crystal and two reflectors, the 532 nm laser pulse is modulated into the burst mode with a repetition rate of 500 MHz. A streak tube camera is used as the signal receiving apparatus. An underwater target detection experiment has been carried out. The results indicate that this lidar-radar could emit a stable and powerful modulated signal, which greatly increases the underwater detection range. The cooperation of the streak tube imaging and modulated laser source for underwater target detection experiments is the first attempt in this field. The clear 3-D and 4-D images of the target underwater across 20 m are obtained in the experiments and the spatial resolution of 9 mm can be achieved. ? 2021
Accession Number: 20212410502905
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Record 281 of
Title:Error compensation of laser tracker in multi-station measurement
Author(s):Wang, Ruiyan(1,2); She, Wenji(1)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 12069 Issue: DOI: 10.1117/12.2606674 Published: 2021
Abstract:In order to improve the multi station measurement accuracy of laser tracker, aiming at the problem that the measurement error of laser tracker restricts the transfer accuracy, the compensation method of measurement error of single laser tracker in multi-station measurement is studied in this paper. The compensated coordinate measurement values are substituted into the coordinate transformation model, and the weighted total least square method is used to iteratively solve the transfer parameters. The results are verified by Matlab simulation experiments. The results show that the mean square errors of coordinate points before and after compensation are respectively 0.4358μm and 0.2920μm. The data show that the measurement accuracy of the laser tracker is improved by 30%. ? COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.
Accession Number: 20220211444601
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Record 282 of
Title:Tumor imaging of a novel Ho3+-based biocompatible NIR fluorescent fluoride nanoparticle
Author(s):Fan, Q.(1,2); Zhang, G.W.(4); Peng, B.(1,3)
Source: Journal of Luminescence Volume: 235 Issue: DOI: 10.1016/j.jlumin.2021.118007 Published: July 2021
Abstract:Cancer has become the leading cause of death for its high incidence and mortality. Early diagnosis and treatment are essential for the inhibition of tumor growth. In this work, A biocompatible, nontoxic, near-infrared fluorescent tumor targeting nanoparticle KHLF(K5HoLi2F10) was prepared by a delicate method for the early diagnosis of tumor. The surface functionalization of the nanoparticle endows it with good water solubility and biocompatibility. Covalent binding to folic acid provides it with the ability to target HeLa cells. After modification, this nanoparticle can still maintain high fluorescence intensity and it can be detected in 2 cm thick pork tissue. We carried out biodistribution imaging, organs imaging and tumor targeting imaging experiments to characterize its imaging ability in vivo. The results show that this nanoparticle could accurately accumulate in HeLa tumor and generate significant fluorescence signal, which confirms the nanoparticle has great potential as a efficient biocompatible fluorescent contrast agent for tumor diagnosis. ? 2021 Elsevier B.V.
Accession Number: 20210910003209
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Record 283 of
Title:Research on nutation coupling method for space laser communication
Author(s):Zhao, Yue(1,2); Han, Junfeng(2); Meng, Xiangsheng(2); Chang, Zhiyuan(2); Xie, Xiaoping(2)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 12060 Issue: DOI: 10.1117/12.2606800 Published: 2021
Abstract:With the rapid development of the times, traditional communication methods such as microwave communication have been difficult to meet the needs of high-speed and high-capacity communication. People begin to look for new communication technologies to replace the existing communication methods. Laser communication has the advantages of high bandwidth, small terminal volume and good security. In the process of space laser communication, the coupling of space light to single-mode fiber is one of the difficulties. In the process of practical application, external jitter (atmospheric turbulence, platform vibration, etc.) makes the focus spot offset from the end face of the optical fiber, greatly reduces the energy coupled into the single-mode optical fiber, and seriously affects the communication quality. Applying the mature optical fiber communication technology to space laser communication can not only improve the transmission rate of the link, but also improve the communication quality and simplify the system composition. Based on laser nutation, aiming at the problem of space optical coupling into single-mode fiber in space laser communication, this paper analyzes the influence of alignment error on coupling efficiency. The lateral deviation has the greatest influence. In this paper, a laser nutation coupling system model based on the fast mirror is built. The model is based on the principle of mode field matching. The nutation signal of the nutation fast mirror is used as the modulation signal, and the optical power output by the photodetector is used as the feedback for calculation. The fast mirror is controlled in real time to compensate the transverse deviation. The algorithm flow of laser nutation is described, the simulation model is built, and the feasibility of the algorithm is verified. Based on different algorithm parameters such as nutation radius and convergence step, the relationship between parameter value and algorithm performance is obtained. ? 2021 SPIE.
Accession Number: 20220211446980
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Record 284 of
Title:Sequential three-branch decision method based on Bayesian principle
Author(s):Zeng, Ke(1,2); Ran, Junfeng(2)
Source: Proceedings of the 33rd Chinese Control and Decision Conference, CCDC 2021 Volume: Issue: DOI: 10.1109/CCDC52312.2021.9601833 Published: 2021
Abstract:In this paper, the sequential three-branch decision method based on Bayesian principle is applied to face image recognition to realize the minimum risk decision. Adding a pending area to the traditional two-branch decision can minimize the decision cost when the misclassification cost is imbalanced and the feature information of the sample is temporarily insufficient. In addition, the acquisition of sample feature information is not unlimited. Although each feature information obtained can reduce the cost of misclassification of decision, it is also necessary to consider the increased test cost of each feature information obtained. This paper used the Bayesian principle to realize the dynamic balance of them to achieve the minimum total decision cost (misclassification cost and test cost). In this paper, 2DPCA was used to obtain the granular features of face images, and experiments were conducted on face databases such as AR and PIE to verify the effectiveness of the sequential three-branch decision method based on Bayesian principle. ? 2021 IEEE.
Accession Number: 20220911715508
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Record 285 of
Title:Automatic checkerboard corner detection combined with gray features and energy minimization (ADGE)
Author(s):Wang, YuanZhang(1,2); Gao, Xiaohui(1)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 12065 Issue: DOI: 10.1117/12.2601236 Published: 2021
Abstract:In the camera calibration process, the checkerboard pattern has a wide range of applications. Aiming at the current checkerboard corner detection algorithms that have missed and misdetected situations, this paper proposes an automatic checkerboard corner detection algorithm that combines gray-scale features and energy minimization(ADGE). The ADGE first uses the proposed two sets of gray-level symmetry operators to process the image separately to extract the candidate corner points, and then uses the regional block mode to dynamically search for the local maximum value of the candidate corner points. It further constructs a reaction function to linearly solve the sub-pixel coordinates, and finally extracts all checkerboard corner points and sorts them by minimizing the energy function. Experimental results show that the corner points extracted by the ADGE have no missed and false detection, and the corner reprojection accuracy is 0.1298 pixels. The ADGE can meet the requirements of camera calibration and provide it with high-precision data. ? 2021 SPIE.
Accession Number: 20220211438051
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Record 286 of
Title:Three-dimensional reconstruction technique based on triangular phase shift and complementary gray code
Author(s):Gao, Ruixue(1,2); Zhang, Pengchang(1); Wang, Pengchong(1); Ling, Xi(1,2)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 12065 Issue: DOI: 10.1117/12.2606547 Published: 2021
Abstract:Structured light 3D reconstruction technology has the advantages of non-contact, low cost and high reliability, and is widely used in industrial parts defect detection, cultural relics 3D digitization and other fields. As the core part of structured light, coding method is the key element to obtain 3D scene information, which directly affects the accuracy of 3D reconstruction. The combination of gray coding and phase shifting is a typical method for 3D shape measurement. However, due to the complexity of sinusoidal fringe calculation, and the fringe pattern boundary cannot be strictly aligned, there is a step change problem, which limits the application of this method in the field of real-time high-speed three-dimensional measurement. In this paper, the phase shift method of triangular wave and gray coding are combined to measure the 3D morphology. The triangular wave function only uses two raster images and the phase information can be obtained by simple intensity ratio calculation. The binary defocus technique can shorten the projection time, but it blurs the edge boundary of gray code and aggravates the step problem of reconstruction of object surface. In order to solve this problem, the complementary gray code whose fringe width is half of the sinusoidal fringe period is used to correct the period deviation. The experimental results show that the proposed method can reduce the number of fringe projection, simplify the calculation steps and shorten the time of data processing, so it is feasible. ? 2021 SPIE.
Accession Number: 20220211438130
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Record 287 of
Title:The design and fabrication of freeform lenses for generating complex illumination patterns on curved surfaces
Author(s):Zhang, YuPeng(1,2); Mao, Xianglong(1); Xie, Yongjun(1); Li, Jinpeng(1); Wang, Fengbiao(1); Gao, Rong(1)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 11761 Issue: DOI: 10.1117/12.2586416 Published: 2021
Abstract:Freeform optics have been found in a variety of beam shaping designs. However, they are typically used to form prescribed illumination patterns on a planar surface. In this paper, we will demonstrate a ray mapping based method to design smooth freeform lenses to form complicated illumination distributions on curved surfaces. The ray mapping between the source and target is established by solving an optimal mass transportation problem which is governed by the Monge-Ampére partial differential equation. Then, the freeform lens is constructed by a geometric method based on the optimal ray mapping. Finally, the performance of the lens is verified by Monte Carlo ray tracing simulation in Zemax OpticStudio software. To show the effectiveness of the proposed method, several freeform lenses are designed as examples for a collimated light source to generate different illumination patterns on different curved surfaces. A freeform lens is also fabricated and experimented. ? COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.
Accession Number: 20210509874593
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Record 288 of
Title:Analysis of the internal stray radiation in infrared imaging system based on ambient temperature
Author(s):Shen, Lamei(1,2); Li, Zhiguo(1,2); Liu, Kai(1,2)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 12061 Issue: DOI: 10.1117/12.2606696 Published: 2021
Abstract:When the infrared imaging system measuring the radiation characteristics of the target, the internal stray radiation is an important factor affecting the measurement results, and the environmental temperature will directly lead to the change of the internal stray radiation. This paper analyzes the phenomenon of the gray drift of the system output caused by the environmental temperature change, and derives the functional relationship between the drift amount and the ambient temperature. A simulation analysis model of internal stray radiation was established to verify the theoretical analysis. Copyright ? 2021 SPIE.
Accession Number: 20220211450723
