Journals >Acta Photonica Sinica
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2021
Volume: 50 Issue 4
25 Article(s)
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Atmospheric and Oceanic Optics
Comparative Analysis of Metastable Helium Resonance Fluorescence Lidar Systems
Jiaxin LAN, Ruocan ZHAO, Tingyu PAN, Xianghui XUE, Tingdi CHEN, Dongsong SUN, and Zimu LI
The pulsed lidar system and continuous lidar system are improved by redesigning the parameters considering more details of the systems and choosing the more appropriate equipment according to limitations of the systems. After the simulation of the return signals， these two kinds of lidar systems are compared in SNR andThe pulsed lidar system and continuous lidar system are improved by redesigning the parameters considering more details of the systems and choosing the more appropriate equipment according to limitations of the systems. After the simulation of the return signals， these two kinds of lidar systems are compared in SNR and difficulty of implementation. The results show that the pulsed lidar is more suitable for measuring the metastable Helium density of thermosphere and exosphere..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 46 (2021)
Measurement and Concentration Inversion of Ozone in Golmud by Laser Heterodyne Spectrometer
Jun HUANG, Yinbo HUANG, Xingji LU, Zhensong CAO, Gang QI, and Zihao YUAN
In order to measure the ozone concentration， a 3.3 μm laser heterodyne spectrometer for field observation was built and the spectral resolution was measured to be 0.004 cm-1. The ozone spectrum was measured at Golmud in Qinghai Province by the 3.3 μm laser heterodyne spectrometer， and the ozone concentration was inversIn order to measure the ozone concentration， a 3.3 μm laser heterodyne spectrometer for field observation was built and the spectral resolution was measured to be 0.004 cm-1. The ozone spectrum was measured at Golmud in Qinghai Province by the 3.3 μm laser heterodyne spectrometer， and the ozone concentration was inversed by using the optimal estimation algorithm. During the field observation， the average column concentration of ozone was inversed to be 241.7 DU， the column concentration increased about 4 DU/h. The results show that the laser heterodyne spectrometer combines with the optimal estimation algorithm is capable of measuring the ozone concentration of the whole atmosphere at the plateau， and has important applications for the environment， meteorology and laser atmospheric transmission assessment..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 57 (2021)
Research on Influence of Aberration and Turbulence on Performance of 90° Space Optical Hybrid
Xiyu GONG, Peng ZHANG, Xiaojie WU, Hang NAN, Daifang GUO, Chao WANG, and Shoufeng TONG
The optical signal is distorted in the atmospheric turbulence， after passing through the defective optical antenna and the space optical hybrid， there are problems of low hybrid efficiency and jitter. According to the influence of 90° space optical hybrid with space output and single-mode output， the hybrid efficiThe optical signal is distorted in the atmospheric turbulence， after passing through the defective optical antenna and the space optical hybrid， there are problems of low hybrid efficiency and jitter. According to the influence of 90° space optical hybrid with space output and single-mode output， the hybrid efficiency model of space optical hybrid with primary aberration is derived. Then the influence of aberration and turbulence on hybrid efficiency is studied. The simulation results show that for the space output 90° space optical hybrid with a target radius of 50 μm of the detector， the tilt， spherical aberration， defocus，coma，and astigmatism with aberration of 0.2λ cause the hybrid efficiency to decrease by 9.8%， 0.6%， 0.36%， 0.02% and 0.01%， respectively. Astigmatism and coma have no effect on the hybrid efficiency. For the single-mode output hybrid， the tilt， astigmatism， defocus， coma， and spherical aberration with aberration of 0.2λ cause the hybrid efficiency to decrease by 14.11%， 8.39%， 6.35%， 2.63% and 1.13%， respectively. When the turbulence intensity Cn2<6.4×10-17 m-2/3， the hybrid efficiency of the spatial output type is more than 0.19 higher than that of the single-mode output 90° space optical hybrid， and when the turbulence intensity Cn2>6.4×10-16 m-2/3 ， the hybrid efficiency of the two is close to zero. Finally， the space output and single-mode output optical hybrid are designed and processed， and the performance test platform is built. For the space output hybrid with a detector target surface radius of 50 μm， the tilt， spherical aberration， and defocus of 0.2λ cause the hybrid efficiency to decrease by 52%， 10%， and 6%； for the single-mode output hybrid， the tilt， astigmatism and defocus with aberration of 0.2λ cause the hybrid efficiency to decrease by 65%， 24% and 11%. Other aberrations have no effect on the hybrid efficiency.The experimental results of turbulence on the hybrid performance show that the standard deviation of the intermediate frequency signal value of the space output optical hybrid is 21.388， which is much lower than that of single-mode output standard deviation 247.442..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 66 (2021)
Performance Optimization and Experimental Research of Continuous Wave Coherent Wind Lidar
Wuhao YANG, Pu ZHANG, Xinfeng YANG, Qimin CHEN, and Wei ZHAO
Based on the requirement of wind velocity measurement， an all-fiber doppler coherent wind lidar system is built with continuous wave laser source at band 1 550 nm. It is analyzed theoretically for the Carrier-to-noise ratio function of the continuous wave coherent lidar and the weighing function of the wind velocity atBased on the requirement of wind velocity measurement， an all-fiber doppler coherent wind lidar system is built with continuous wave laser source at band 1 550 nm. It is analyzed theoretically for the Carrier-to-noise ratio function of the continuous wave coherent lidar and the weighing function of the wind velocity at different focusing distance on the basis of the lidar equation. A vari-focusing optical antenna with the focusing distance range from 5 m to 200 m is designed and fabricated according to the requirement of wind detection. The optical beam expanding module adopts the Galilean refractive structure with the beam expanding ratio as 23 and the optical quality is close to the diffraction limit. The calibration test is executed by using a rotating motor disk. The rotation speed range of the disk is from －3 000 r/min to +3 000 r/min. The diameter of the disk is 26 cm. While the doppler frequency shift of the line of sight velocity is positive and negative， the correlation coefficients between the velocity measurement data of the lidar system and the theoretical calculation result are 0.998 and 0.993. At the same time the standard deviations of velocity are 0.151 m/s and 0.229 m/s， respectively. The wind lidar is then used to measure the atmospheric wind speed. It works correctly to apply the wind lidar to measure the atmospheric wind velocity..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 81 (2021)
Detectors
Influence of Microchannel Plate Structure Parameters on Noise Factor
Xiaofeng LI, Zhengjun ZHANG, Xiaoqing CONG, Hui FENG, Yaohong QIAN, and Jiaojiao LI
The influences of structure parameters of microchannel plate， such as opening area ratio， thickness， electrode depth， ion barrier film and input enhancement film on noise factor， were studied by comparative measurement method. The results show that the noise factor decreases with the raising of opening area ratio； incrThe influences of structure parameters of microchannel plate， such as opening area ratio， thickness， electrode depth， ion barrier film and input enhancement film on noise factor， were studied by comparative measurement method. The results show that the noise factor decreases with the raising of opening area ratio； increases with the raising of thickness； increases with the raising of input electrode depth； increases by ion barrier membrane； decreases by the input enhancement film. The influence of ion barrier film on noise factor is the most， and the influence of thickness on noise factor is the least. The structure parameters of microchannel plate not only affect the noise factor， but also affect other parameters such as gain and uniformity. In order to reduce the noise factor of microchannel plate， the most feasible method is to increase the opening area ratio to 68 %， and then make a layer of MgO2 on the input end of microchannel plate. This will reduce the noise factor of microchannel plate close to 1 behaved in the ideal microchannel plate..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 135 (2021)
Spatio-temporal Resolution Studies on a Synchronous Streak Tube
Liping TIAN, Lingbin SHEN, Lin CHEN, Lili LI, Ping CHEN, and Jinshou TIAN
A synchronous streak tube capable of providing high spatial resolution， high temporal resolution and large working area is numerically designed and experimentally demonstrated. In this paper， a 3-D model developed to systematically and comprehensively analyze the dependence of the physical temporal resolution on the acA synchronous streak tube capable of providing high spatial resolution， high temporal resolution and large working area is numerically designed and experimentally demonstrated. In this paper， a 3-D model developed to systematically and comprehensively analyze the dependence of the physical temporal resolution on the accelerating voltage， the spatial resolution on the deflector-to-cathode distance， the dynamic spatial resolution and temporal resolution on the scanning velocity. Finally， geometry and electric parameters of dDC=100 mm， Ug=700 V， and Tscreen= 0.5 ns are proposed to optimize the streak tube performances. The numerical simulations show that the static spatial resolution is higher than 25 lp/mm @ MTF=10% and the dynamic spatial resolution is higher than 16 lp/mm @ MTF=10% over the whole effective photocathode area of 18 mm×2 mm. And， the simulated temporal resolution is better than 5.6 ps at Tscreen=0.5 ns. Furthermore， the photocathode radiant sensitivity can reach 51 mA/W at the wavelength of 400 nm. The tested static spatial resolution is as high as 25 lp/mm @ CTF=13%..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 143 (2021)
Fiber Optics and Optical Communications
Analysis of Underwater Wireless Optical Transmission Characteristics Based on Monte Carlo Method
Qiong WU, Bo WANG, Tao WANG, Renjiang ZHU, Peng ZHANG, and Lijie WANG
Underwater wireless optical transmission faces the problems of power attenuation and time domain width enlargement， the long-distance transmission characteristics of blue-green light are also more difficult to test. Monte Carlo method is used to investigate the process of underwater Gaussian beam， the effects of channeUnderwater wireless optical transmission faces the problems of power attenuation and time domain width enlargement， the long-distance transmission characteristics of blue-green light are also more difficult to test. Monte Carlo method is used to investigate the process of underwater Gaussian beam， the effects of channel parameters such as water type， attenuation distance and divergence angle on the received power and impulse response are taken into account， power distribution on the receiving surface with different seawater types and transmission distances under small divergence is also numerically compared. The simulation results show that the received power decreases gradually and the time-domain width expands greatly with the increase of seawater attenuation coefficient， attenuation distance and divergence angle， among them， the influence of divergence angle on the transmission distance of turbid harbor water above 10 m is small， while the width of time domain changes from 0.32 ns to 0.8 ns with the increase of divergence angle. Although the transmission distance is doubled， the power similarity is still up to 99% in pure sea water and clear ocean water. Then based on the difference of seawater attenuation coefficient， we propose the power similarity and area ratio to analyze underwater long-distance transmission， so as to obtain the long-distance transmission characteristics more efficient and quicker..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 22 (2021)
High-resolution Microwave Frequency Dissemination via 56 km Optical Fiber Based on Microwave Phase Compensation
Honglei QUAN, Wenyu ZHAO, Wenxiang XUE, Yan XING, Haifeng JIANG, Wenge GUO, and Shougang ZHANG
This paper reports a microwave frequency dissemination experiment over a 56 km-long-fiber link in the laboratory， exhibiting frequency instabilities of 1.8×10-15/s and 4×10-18/104s. The phase perturbation accumulated along the fiber link is detected by comparing the round-trip signal with the reference signalThis paper reports a microwave frequency dissemination experiment over a 56 km-long-fiber link in the laboratory， exhibiting frequency instabilities of 1.8×10-15/s and 4×10-18/104s. The phase perturbation accumulated along the fiber link is detected by comparing the round-trip signal with the reference signal. By controlling the phase of the transmitted signal in real time， the phase perturbation along the fiber link is compensated. Different modulation frequencies are used to avoid stray reflection effect. To improve the phase noise of the detection signal， we also implemented dispersion compensation..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 32 (2021)
Measurement of Optical Fiber Refractive Index Distribution Based on White Light Scanning Interferometry
Min LI, Wuzhou SONG, Wei ZHAN, Rongyao WU, and Jinhua QIU
A method for measuring the refractive index distribution of optical fibers is presented， which uses the white light scanning interference technology and builds the same structure on the reference mirror as the optical fiber sample to overcome the limitation of the short white light coherence length， optimizes the opticA method for measuring the refractive index distribution of optical fibers is presented， which uses the white light scanning interference technology and builds the same structure on the reference mirror as the optical fiber sample to overcome the limitation of the short white light coherence length， optimizes the optical path and improves the contrast between the interference fringes. For white light interference signals， Morlet wavelet which has Gaussian distribution like envelope of white light interference fringes is used as the mother wavelet of wavelet transform for fitting processing， and the relative height between the fiber and the matching fluid with known refractive index is obtained. The refractive index distribution of optical fiber can be obtained by calculation， and fitting the obtained data with the classical function of the refractive index distribution of the fiber core， the coefficients of determination of the multi-mode fiber and single-mode fiber are 0.997 2 and 0.996 4 respectively. Finally， the experimental results are compared with the official parameters， and the error is 0.01%， which shows that this method has a high precision and can be used to measure the refractive index of optical fiber..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 39 (2021)
Image Processing
Infrared Image Fusion Algorithm Selection Based on Joint Drop Shadow of Possibility Distributions
Linna JI, Xiaoming GUO, Fengbao YANG, and Yaling ZHANG
Aiming at the actual fusion needs of heterogeneous difference features collaborative optimization are often involved for dual-mode infrared images fusion， and the existing difference feature attributes cannot be targeted to adjust algorithms to drive fusion effectively， resulting in poor fusion effect， a method of infrAiming at the actual fusion needs of heterogeneous difference features collaborative optimization are often involved for dual-mode infrared images fusion， and the existing difference feature attributes cannot be targeted to adjust algorithms to drive fusion effectively， resulting in poor fusion effect， a method of infrared image fusion algorithm selection based on joint drop shadow of possibility distributions is proposed. Firstly， the fusion effectiveness of the difference feature amplitude of the dual-mode infrared image is calculated， and the probability density distribution of the difference feature amplitude and the distribution of the frequency attribute based on K-nearest neighbor method is obtained. Then the difference feature weight function through difference feature amplitude attribute and frequency attribute is constructed， and the possibility distribution synthesis between the heterogeneous difference feature weight function and fusion algorithms is established to obtain the joint drop shadow of the fusion effectiveness of heterogeneous difference feature weight function and the fusion algorithms. Finally， the fusion performance index is constructed to select the optimal fusion algorithm dynamically. The experimental results show that the optimal fusion algorithm selected by this method on the ranking score index is significantly higher than other algorithms， which the feasibility of applying joint drop shadow of possibility distributions in the optimal selection of dual-mode infrared images fusion algorithm is verified ..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 228 (2021)
Feature Extraction of Hyperspectral Image Based on Sparse Representation and Learning Graph Regularity
Minghua ZHANG, Hongling LUO, Wei SONG, Dongmei HUANG, Qi HE, and Cheng SU
Traditional local feature extraction algorithms are difficult to determine neighborhood parameters， and they only consider the single structure information of the data， which ignore important information. To solve the above problems， a Local Discrimination and Global Sparse Preservation Projection Algorithm（LDGSPP） basTraditional local feature extraction algorithms are difficult to determine neighborhood parameters， and they only consider the single structure information of the data， which ignore important information. To solve the above problems， a Local Discrimination and Global Sparse Preservation Projection Algorithm（LDGSPP） based on sparse representation and learning graph regularity is proposed. The algorithm firstly applies a learning-based graph regularizer to the sparse representation model. Then the improved sparse representation model is used to reveal the local linear structure of the sample data adaptively. The local discriminant model global integration algorithm is used to extract the discriminant information of the local linear structure. The new sparse graph constructed by the improved sparse representation model is used to reveal the global sparse structure of data. The local discriminant structure and the global sparse structure of the data are preserved in the low dimensional feature space. 1-nearest neighbors and support vector machine classifier are used to evaluate the experimental results. The experiments on PaviaU and Indian Pines show that LDGSPP achieves the best performance compared with the comparison algorithm. As global and local discriminant information is extracted， the ground object classification accuracy of hyperspectral images is effectively improved..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 241 (2021)
Hyperspectral Anomaly Detection Based on 3D Convolutional Autoencoder and Low Rank Representation
Bangyong SUN, Zhe ZHAO, Bingliang HU, and Tao YU
Due to the challenge of high dimensionality， insufficient utilization of spatial-spectral information and limited local structure property expression in hyperspectral images， a hyperspectral anomaly detection algorithm based on 3D convolutional autoencoder and low rank representation is proposed in this paper. Firstly，Due to the challenge of high dimensionality， insufficient utilization of spatial-spectral information and limited local structure property expression in hyperspectral images， a hyperspectral anomaly detection algorithm based on 3D convolutional autoencoder and low rank representation is proposed in this paper. Firstly， the spectral-spatial features of hyperspectral images are extracted by 3D convolutional autoencoder. In order to precisely represent the local similarity， a new loss function is proposed to constrain the central pixel and it's surrounding pixels to extract more discriminative features. And then， the Density Based Spatial Clustering of Applications with Noise （DBSCAN） algorithm is used to construct the background dictionary， and the abnormal region is separated by low rank representation on the feature map. Finally， the detection result is obtained by fusing the reconstruction error obtained by 3D convolution autoencoder and abnormal region detection result. We carry out objective and subjective anomaly detection experiments on two real hyperspectral datasets. The results demonstrate that the proposed algorithm detect abnormal targets more accurately compared with other algorithms..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 254 (2021)
Instrumentation, Measurement and Metrology
Thermal Characteristics Analysis and Verification of Primary Supporting Structure for Spaceborne Camera Based on Low Volume SiC/Al Primary Mirror Frame
Weiyan LI, Qunbo LÜ, Yangyang LIU, Zheng TAN, Jianwei WANG, Na ZHAO, Linlin PEI, Jianying SUN, and Xinwen CHEN
Based on the weight constraint of micro-satellite platform on high resolution camera， taking the digital super-resolution camera of high-resolution micro-nano satellite （CX6-02） as an example， the integrated camera topology optimization design and experimental verification are carried out with primary mirror frame is tBased on the weight constraint of micro-satellite platform on high resolution camera， taking the digital super-resolution camera of high-resolution micro-nano satellite （CX6-02） as an example， the integrated camera topology optimization design and experimental verification are carried out with primary mirror frame is taken as the primary supporting structure. The Zernike polynomial calculation and opto-mechanical thermal integration simulation are carried out， the results show that the low-volume SiC/Al primary mirror frame is effective as the supporting structure of the spaceborne camera. The thermo-optic data and on-orbit imaging results show that the experimental data of the spaceborne camera with the main supporting function of the low-volume SiC/Al primary mirror frame is consistent with the simulation data， and the performance is stable. It can provide a reference for the lightweight design and development of spaceborne cameras based on low-volume SiC/Al in the future..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 207 (2021)
Active Alignment Method of Telescope Based on Star Ellipticity of Multi Field of View
Bo LI, Xiangyan YUAN, Zhengyang LI, and Haiping LU
The image quality of an astronomical telescope degrades in observations if the misalignment of optical elements exists. The degredation is more severe in astronomical systems with large aperture and fast focal ratio. To solve this problem， the paper proposes an active alignment method for routine observations of telescThe image quality of an astronomical telescope degrades in observations if the misalignment of optical elements exists. The degredation is more severe in astronomical systems with large aperture and fast focal ratio. To solve this problem， the paper proposes an active alignment method for routine observations of telescopes. The proposed method here aims to maintain the image quality by quasi-real time corrections on both the position and attitude of the telescope secondary mirror via the computation of star images. Considering the ellipticity of the star images in multi-field-of-view， the proposed method uses the particle swarm optimization to iteratively solve the misalignment of the telescope optics， so as to correct the lower-order aberrations induced by the misalignment. The simulation in the paper is carried on with 1.6 m multi-channel photometric survey telescope， proving that the residual error of misalignment of the secondary mirror is less than 1%， within the tolerance range. Further simulation and experiment are carried out on the Three Antarctic Survey Telescopes （AST3-3） for the verification， proving that the proposed method is able to precisely solve the misalignment of the telescope optics..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 218 (2021)
Lasers and Laser Optics
Effect of Laser Shock on Microstructure of the Repair Layer of E690 High Strength Steel by Laser Cladding
Yupeng CAO, Shuai WANG, Weidong SHI, Ming QIU, Guoran HUA, and Bin LI
In order to study the effect of laser shock on microstructure of the repair layer of E690 high strength steel by laser cladding， a special metal powder was selected to perform laser cladding on ready-made pits of E690 high strength steel， and the laser cladded layer was subjected to surface mechanical strengthening treIn order to study the effect of laser shock on microstructure of the repair layer of E690 high strength steel by laser cladding， a special metal powder was selected to perform laser cladding on ready-made pits of E690 high strength steel， and the laser cladded layer was subjected to surface mechanical strengthening treatment by laser shock processing. The microstructure and surface residual stress of the repair layer were characterized by a scanning electron microscope， transmission electron microscope and X-ray stress analyzer. The results show that， after laser cladding repair， the repair layer presents an equiaxed grain structure. There is a good metallurgical bond between the laser cladded layer and the substrate. The residual stress on the surface of the repair layer is in a state of compressive stress. Following the laser shock processing， the cross-sectional grains on the repair layer are refined and a large number of deformation twins are observed. Coarse grains of the cladded layer are separated by parallel twin boundaries， which plays an important role in grain refinement process of the laser cladded layer. The dislocations on the surface of the sample experienced a slip on the ｛110｝ slip surface， forming dislocation entanglements around the grain boundaries. After laser shock， the value of surface residual compressive stress of laser cladded layer increases by 1.1 times compared with that prior to the laser shock processing..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 91 (2021)
Laser Fabrication and Performance of Periodic Microstructure on Polycrystalline Silicon Surface
Tiantian LI, Yaoning SUN, Li ZHANG, Guojian WANG, Tiandai JIA, and Aixin FENG
In order to reduce the reflectivity of incident light on the surface of polysilicon and improve the photoelectric conversion efficiency of solar cells， a UV nanosecond laser is adopted to prepare micro-dimples with different depths and pore pitch on the surface of polysilicon， and the effect of texture topography on reIn order to reduce the reflectivity of incident light on the surface of polysilicon and improve the photoelectric conversion efficiency of solar cells， a UV nanosecond laser is adopted to prepare micro-dimples with different depths and pore pitch on the surface of polysilicon， and the effect of texture topography on reflectivity and photoelectric conversion efficiency is studied. The depth of the micro-dimples are controlled by the laser frequency while the pore pitch of the micro-dimples are changed by the arrangement of the micro-dimples. The reflectivity of polysilicon samples and surface morphology of micro-dimples are observed by optical fiber spectrometer and laser scanning confocal microscope， respectively； The reflection model of incident light is established using the PC1D software and the short-circuit current and open-circuit voltage of polysilicon with different pore pitch are simulated， the photoelectric conversion efficiency and fill factor are calculated subsequently. Research shows that different frequencies （300 kHz， 200 kHz， 150 kHz， 50 kHz） and micro-dimples arrangements （300×300， 310×310， 350×350， 400×400） have significant effects on the reflectivity and photoelectric conversion efficiency of polysilicon. As the frequency increases， the reflectivity of the polysilicon sample decreases first， then increases and finally remains stable； as the density of the lattice arrangement increases， the photoelectric conversion efficiency of the polysilicon sample gradually increases. The experiment result shows that when the laser frequency is 150 kHz and the micro-dimples distribution is 400×400， the topography of micro-dimples on polysilicon surface are well formed. And the average reflectivity is 3.32%， the photoelectric conversion efficiency of the polysilicon cell is 18.80%， which is 25.9% improvement compared with the untextured polysilicon cell..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 102 (2021)
Machine Vision
Camera Calibration Method with Multi-condition Constraints Based on Laser Points
Cailin LI, Benya SU, Baoyun GUO, Zhiyong WANG, and Fuhong ZHU
A camera calibration method based on multi-condition constraints of laser point cloud is proposed to overcome the dependence of camera calibration on the 2D/3D calibration field. The initial camera parameters are obtained by bundle adjustment from the multi-view image obtained by the camera. Then， based on the collineaA camera calibration method based on multi-condition constraints of laser point cloud is proposed to overcome the dependence of camera calibration on the 2D/3D calibration field. The initial camera parameters are obtained by bundle adjustment from the multi-view image obtained by the camera. Then， based on the collinear equation， the mathematical model of the multi-condition constraints camera calibration is established by using the position relationship between the image point cloud and its nearest laser point cloud. Furthermore， the least square method with inequality constrains is used to calculate the camera parameters iteratively. The camera calibration accuracy of the method is compared with that of the 3D control field. The experiment results show that it is equivalent to the calibration accuracy based on the 3D control field. The average error difference between the two laser point cloud reflection is less than 0.1 pixel， which further verifies the feasibility of the method without traditional control field..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 172 (2021)
Research on Visual Odometry Based on Catadioptric Panoramic Camera
Yu ZHANG, Xiping XU, Ning ZHANG, Yaowen LÜ, and Yi LU
In order to realize the real-time positioning of the catadioptric panoramic camera， a visual odometry method based on the feature point method that can be applied to the catadioptric panoramic camera was proposed. the initialization module for the projection model of the catadioptric panoramic camera was designed for tIn order to realize the real-time positioning of the catadioptric panoramic camera， a visual odometry method based on the feature point method that can be applied to the catadioptric panoramic camera was proposed. the initialization module for the projection model of the catadioptric panoramic camera was designed for the initialization of the camera pose. In the initialization module， a spherical epipolar geometry suitable for catadioptric panoramic cameras was proposed， and the posture change relationship between two frames of images during the initialization process was calculated through the spherical epipolar geometry. In order to verify the robustness and accuracy of the algorithm， in the same scene， the algorithm in this paper was compared with the visual mileage calculation method using the feature point method of the pinhole camera. The results show that， in the case of using catadioptric panoramic camera， the accuracy of visual odometry in outdoor scenes and indoor scenes improves by 38% and 50%..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 182 (2021)
Materials
Optically Transparent Hybrid Metasurfaces for Low Infrared Emission and Wideband Microwave Absorption
Cuilian XU, Yueyu MENG, Jiafu WANG, Mingbao YAN, Wenjie WANG, Jinming JIANG, and Shaobo QU
Based on the transparent conductive material Indium Tin Oxide （ITO） and highly transparent Polyethylene Terephthalate （PET）， optically transparent ultra-wideband radar and infrared compatible stealth hybrid metasurfaces were achieved. Two specically designed optically transparent metasurfaces were combined to realize rBased on the transparent conductive material Indium Tin Oxide （ITO） and highly transparent Polyethylene Terephthalate （PET）， optically transparent ultra-wideband radar and infrared compatible stealth hybrid metasurfaces were achieved. Two specically designed optically transparent metasurfaces were combined to realize radar and IR bi-stealth. One was designed to control the microwave absorption though properly modifying the impedance and resonance peaks of the meta-atom. The other was empolyed to control the IR radiation.The absorptivity in the microwave band 8.0~32.0 GHz band is greater than 90%， and its infrared stealth performance and heat radiation characteristics are further studied..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 153 (2021)
Alkali Metal Ion， Gd3+， Ce3+ Co-doped Lu3Al5O12 Optical Properties of Ceramic Powder
Yunfeng BAI, Linxiang WANG, Qing LI, and [in Chinese]
（GdxMyLu0.99-x-y）3Al5O12：1%Ce3+（x=0，0.01，0.25，0.5，0.75，y=0，0.005，0.01，0.02，0.05，0.1， M=Li+，Na+，K+，Cs+） series ceramic powders were synthesized by high temperature solid phase method. The microstructure of the sample was characterized by XRD， the excitation spectrum， emission spectrum and fluorescence lifetime of the sa（GdxMyLu0.99-x-y）3Al5O12：1%Ce3+（x=0，0.01，0.25，0.5，0.75，y=0，0.005，0.01，0.02，0.05，0.1， M=Li+，Na+，K+，Cs+） series ceramic powders were synthesized by high temperature solid phase method. The microstructure of the sample was characterized by XRD， the excitation spectrum， emission spectrum and fluorescence lifetime of the sample were measured by FLS920 spectrometer， and the color coordinate of the sample was analyzed by the CIE chromaticity system. XRD results show that the Lu3Al5O12 samples co-doped with different concentrations of alkali metal ions、Gd3+ and Ce3+ are still cubic crystal phases， but with the increase of alkali metal ions， Gd3+ and Ce3+ doping concentrations， the diffraction peaks of the samples shift slightly to a small angle. Under the excitation of 350 nm， compared with the Lu2.97Al5O12：1%Ce3+ sample， the emission intensity of the sample co-doped with Gd3+ at around 511 nm decreased and appeared a significant red shift. With the increase of the doped Gd3+ concentration， the Ce3+ energy level lifetime gradually decreased. The range is 35~60 ns. Compared with the sample doped with 1%Ce3+ and 1%Gd3+， the luminescence intensity of the sample doped with 2%Li+， 2%Na+， 2%K+ and 1%Cs+ increased by 5.1 times and 2.93 times， respectively. At this time， the lifetime of Ce3+ in the sample continued to decrease. When the samples were irradiated under UV lamps with λ=254 nm and λ=365 nm， it was observed that with the increase of Gd3+ doping concentration， the color of the sample changed from dark yellow-green to dark red. The color coordinates show that the light-emitting area of the sample gradually moves from the yellow-green light area to the red light area. After co-doping with alkali metal ions， the sample emits brighter..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 163 (2021)
Optical Devices
Digital Thermo-optic Switch of SOI Waveguide Based on Goos-Hänchen Spatial Shift of Reflected Mode
Zhuo CHEN, Tiancheng LI, Degui SUN, Na SUN, Hongpeng SHANG, and Chen CHEN
With the waveguide corner mirror structure and the effective combination of the Goos-Hanchen （GH） spatial shift and the thermo-optical effect refractive index modulation， a digital thermo-optical switch structure of waveguide reflected mode is proposed. The GH spatial shift is optimized under the condition of a given iWith the waveguide corner mirror structure and the effective combination of the Goos-Hanchen （GH） spatial shift and the thermo-optical effect refractive index modulation， a digital thermo-optical switch structure of waveguide reflected mode is proposed. The GH spatial shift is optimized under the condition of a given incident angle， and the reflected beam has a larger jump under an eigenstate with the GH effect. On a silicon-on-insulator platform with a 1.0 μm thick silicon film， the guided mode eigenstate matching between the single-mode input waveguide and the multimode interference waveguide structure verifies the function of a 1×3 digital optical switch. In experiment， the optical loss caused by the device structure is 0.3 dB， the switching power is 130~150 mW， the switching time is about 50 μs， and the isolation between adjacent output ports is 15 dB. The comparison with the latest results of the Mach-Zehnder interferometer 2×2 thermo-optic switch and the newly emerging plasma effect thermo-optic switch shows the advancement of this digital TO switch..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 111 (2021)
Second-order Microcavity Length Based on Top-emitting Organic Light-emitting Diodes
Zhen WANG, Zhenshan LIANG, Fei XIAO, Jiawen CHEN, Yongsheng LU, Yue PENG, Wenxia ZHANG, and Yuchan WANG
A Top-Emitting Organic Light-Emitting Diodes （TEOLEDs） with the configurations of Al （100 nm）/TAPC （x nm）/TCTA （10 nm）/TCTA：Ir（ppy）3 （10%， 25 nm）/TPBi （30 nm）/LiF （2 nm）/Al （1 nm）/Ag （20 nm）/Alq3 （y nm） （x=30， 130， 160， 170 and 180） （y=20， 40， 60 and 80） was fabricated. The experiments illustrate that photoelectric perA Top-Emitting Organic Light-Emitting Diodes （TEOLEDs） with the configurations of Al （100 nm）/TAPC （x nm）/TCTA （10 nm）/TCTA：Ir（ppy）3 （10%， 25 nm）/TPBi （30 nm）/LiF （2 nm）/Al （1 nm）/Ag （20 nm）/Alq3 （y nm） （x=30， 130， 160， 170 and 180） （y=20， 40， 60 and 80） was fabricated. The experiments illustrate that photoelectric performance of the device can be improved by changing the thickness of the hole transport layer， which make the length of the device microcavity was in the enhancement zone of second-order microcavity effect. Moreover， by changing the light output coupling layer of the device， the transmittance and reflectance of the cathode of the device were changed， which can effectively improve the photoelectric performance of the device. A green TEOLEDs with the best photoelectric performance is achieved when the length of microcavity is 230 nm and the thickness of optical output coupling is 80 nm. The peak luminance， peak current efficiency and peak power efficiency of the TEOLEDs reach 25 960 cd/m2， 19.1 cd/A and 16.01 lm/W， respectively..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 120 (2021)
Bifurcation-tunable Diffractionless Light Propagation in One-dimensional Non-Hermitian Photonic Lattice
Zhenjuan LIU, Haohao WANG, Yanan DAI, Zhiqing ZHANG, Yishan WANG, and Xinyuan QI
The light bifurcation transmission without diffraction in one-dimensional periodic compound photonic lattice was studied theoretically and numerically. When the lattice equals to degenerated Su-Schrieffer-Heeger model， the incident light with the wave number k=±π will bifurcate into two symmetric branches without The light bifurcation transmission without diffraction in one-dimensional periodic compound photonic lattice was studied theoretically and numerically. When the lattice equals to degenerated Su-Schrieffer-Heeger model， the incident light with the wave number k=±π will bifurcate into two symmetric branches without any diffractionand the angles between two beams can be controlled by the coupling J between two lattice sites. In addition， a modulation phase ϕ is introduced. When the non-Hermitian perturbations satisfy the parity-time symmetry， the diffractionless light bifurcation phenomenon with any incident light wave can be realized as long as the incident wave vector k and the modulation phase ϕ respect the expression k+ϕ=±π. Further studies have shown that the next-nearest coupling can control the transmission angle and power division of two branches. This research provides new ideas for the design of optical switches and future all-optical paths..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 128 (2021)
Spectroscopy
Improvement of LVF-based NIR Spectral Sensor on Both Spatial and Time Domains
Xuquan WANG, Songlei HUANG, Pengyu KE, Mengxuan LIU, Zhenli ZHAO, and Jiaxiong FANG
The method to improve performance of Linear Variable Filter （LVF） based spectrometers is proposed and validated. By this means， a compact 512×2 InGaAs spectral sensor with dynamic data fusion on both spatial and time domains is developed. In the spectral sensor， spectral channel is not a single pixel but a group oThe method to improve performance of Linear Variable Filter （LVF） based spectrometers is proposed and validated. By this means， a compact 512×2 InGaAs spectral sensor with dynamic data fusion on both spatial and time domains is developed. In the spectral sensor， spectral channel is not a single pixel but a group of neighboring pixels with multi-frame measurements. The data from two pixel arrays are multiplexed to compensate possible sensor defects such as blind pixels. The wavelength calibration and experimental results show that the proposed methods can significantly reduce the wavelength spacing between spectral channels with the optical resolution limit of LVF..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 191 (2021)
Cross Interference Characteristics of Photoacoustic Spectroscopy Multi-gas Analyzer
Shuai YUAN, Guangzhen WANG, Dehui FU, Ke CHEN, Ran AN, Bo ZHANG, Min GUO, and Guangyin ZHANG
A photoacoustic spectroscopy multi-gas detection system based on infrared heat radiation light source was developed. The broadband mid-infrared thermals radiation source and band-pass filter were used to generate the photoacoustic excitation light. Combined with a small-volume non-resonant photoacoustic cell， the time-A photoacoustic spectroscopy multi-gas detection system based on infrared heat radiation light source was developed. The broadband mid-infrared thermals radiation source and band-pass filter were used to generate the photoacoustic excitation light. Combined with a small-volume non-resonant photoacoustic cell， the time-sharing measurement of multi-component gas concentration was realized. The parameters of the mid-infrared bandpass filter were determined by analyzing the main factors of cross-interference among multi-component gases and the infrared absorption spectrum of target gases. To determine the quantitative relationship of cross interference among the gases to be measured， the photoacoustic spectrometer system was calibrated by using the standard gas， and a humidifier was used to analyze the interference from water vapor. The experimental results showed that the interference levels of C2H2 to CH4 and CH4 to C2H6 reached 10.49 μV/（μL/L） and 18.66 μV/（μL/L） respectively， and the interference between other hydrocarbon gases can be ignored. The responsiveness of CO2 to CO， CH4， C2H2 and C2H4 interference was 1.615 μV/（μL/L）， 0.055 μV/（μL/L）， 0.130 μV/（μL/L） and 0.016 μV/（μL/L）， respectively. In addition， water vapor will cause certain interference to C2H2， CH4， C2H6， C2H4， CO and CO2， and the responsiveness of the interference was 0.591 μV/（μL/L）， 0.421 μV/（μL/L）， 0.071 μV/（ μL/L）， 0.007 μV/（μL/L）， 0.051 μV/（μL/L） and 0.055 μV/（μL/L）. The experimental results indicated that there was a high level of interference when detecting CH4 in C2H2 background， C2H6 in CH4 background， CO in CO2 background， and other target gases in high concentration water vapor background， which should be considered in the measurement process..
Acta Photonica Sinica
- Publication Date: Apr. 25, 2021
- Vol. 50, Issue 4, 198 (2021)
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