Contents
2022
Volume: 42 Issue 9
31 Article(s)
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Atmospheric Optics and Oceanic Optics
Density Reconstruction Method for Complex Flow Based on Light Deflection
Run Zhou, Liang Tang, Ping Li, and Xuhui Huang
The reconstruction of flow field density from the measured value of light deflection angle passing through the disturbed flow field, it is great significance for the in-depth understanding of complex flow phenomena. Based on the deflection angle of light passing through the disturbed flow field obtained by the wind tunThe reconstruction of flow field density from the measured value of light deflection angle passing through the disturbed flow field, it is great significance for the in-depth understanding of complex flow phenomena. Based on the deflection angle of light passing through the disturbed flow field obtained by the wind tunnel video measurement method, the reconstruction method of complex flow density is studied. According to the relationship among density, refractive index, and light deflection angle, the partial differential equation of density with prior information is derived by variational method. The artificial neural network is used to model the measured data, and the error magnification caused by the loss of local peak value is effectively suppressed. The results of numerical simulation and wind tunnel experiments show that the density reconstruction result of this method is obviously better than that of the direct partial derivative method, especially at the peak, this method has higher accuracy in terms of value, which provides a new way for the quantitative analysis of complex flow structure..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0901001 (2022)
Turbulence Models and Daily Variations Obtained by Bidirectional Atmospheric Coherent Length Measurements
Chenxiang Qiu, Zaihong Hou, Xu Jing, Feng He, and Silong Zhang
The atmospheric coherence length is an important parameter for quantitatively describing the intensity of atmospheric turbulence. In this paper, a real-time turbulence intensity distribution mode varying with height can be established by bidirectionally measuring the atmospheric coherence length along the same slope paThe atmospheric coherence length is an important parameter for quantitatively describing the intensity of atmospheric turbulence. In this paper, a real-time turbulence intensity distribution mode varying with height can be established by bidirectionally measuring the atmospheric coherence length along the same slope path, and full-day observation experiments during several days are conducted to verify this method. The accuracy of this method is preliminarily verified by comparing the spatiotemporal distributions of turbulence intensity measured under different weather conditions and analyzing the ratio of atmospheric coherence length measured in multiple days..
Acta Optica Sinica
- Publication Date: May. 20, 2022
- Vol. 42, Issue 9, 0901002 (2022)
Analysis of Polarization Radiation Characteristics of Strong Convective Cloud Clusters
Jiajia Wang, Rufang Ti, Xiao Liu, Honglian Huang, and Xiaobing Sun
The strong convective cloud cluster is one of the important research objects in the meteorology field. The polarization radiation characteristics of strong convective cloud clusters are studied by using the observation data of the atmospheric aerosol multi-angle directional polarimetric camera (DPC), which provides mulThe strong convective cloud cluster is one of the important research objects in the meteorology field. The polarization radiation characteristics of strong convective cloud clusters are studied by using the observation data of the atmospheric aerosol multi-angle directional polarimetric camera (DPC), which provides multi-dimensional information for the identification of strong convective cloud clusters. Taking strong convective cloud clusters, typhoon cloud clusters, and non-precipitation cloud clusters as examples, the research shows that the reflectivity of strong convective cloud clusters is higher than that of non-precipitation cloud clusters, and its spatial distribution is more uniform. Most part of the developing strong convective clusters are ice crystal particles, and only the edge part has liquid water, while the phase distributions in other non-precipitation clouds are quite different. Under similar illumination and observation geometry conditions, the dispersion of the polarization angle spatial distribution of the strong convective cloud clusters is larger than that of non-precipitation cloud clusters, and there is a large difference between the average of polarization angles. The polarization angle image of the strong convective cloud cluster can well characterize its contour characteristics..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0901003 (2022)
Diffraction and Gratings
Diffraction Anomalies and Structural Design of One-dimensional TiO2 Subwavelength Gratings
Maorong Zang, Zhigang Jia, Hailiang Dong, Aiqin Zhang... and Bingshe Xu|Show fewer author(s)
The diffraction anomalies of a one-dimensional TiO2 subwavelength grating (SWG) are studied, which are characterized by leakage mode resonance effect and Rayleigh anomalies. The results show that Rayleigh anomalies and leakage mode resonance effect occurrs for transverse magnetic wave (TM polarization) and transverse eThe diffraction anomalies of a one-dimensional TiO2 subwavelength grating (SWG) are studied, which are characterized by leakage mode resonance effect and Rayleigh anomalies. The results show that Rayleigh anomalies and leakage mode resonance effect occurrs for transverse magnetic wave (TM polarization) and transverse eletric wave (TE polarization) incident under certain parameter conditions. In the case of TM polarized light, the traditional leakage mode resonance effect with narrow band and high diffraction efficiency will occur, while in the case of TE polarized light, due to the superposition of several close leakage mode resonance peaks, the reflection spectra with broad band and high diffraction efficiency will be formed. The diffraction efficiency of a one-dimensional TiO2 SWG is calculated by the rigorous coupled-wave theory (RCWA), and the effects of grating period, height and duty cycle on the reflectivity of the grating are studied. When period, height, and duty cycle of the grating are 0.49 μm, 0.25 μm and 0.34 respectively, the SWG exhibites TE polarization selectivity. The reflectivity at 0.52 μm is close to 1, and the high reflection band (reflectivity is higher than 99.9%) had a width of 26 nm. By optimizing the structural parameters, the manufacturing tolerances of the grating period, duty cycle, and height are 1.6%, 8.3%, and 2.0% respectively, so the SWG can be theoretically used as the reflector of a vertical cavity surface emitting laser..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0905001 (2022)
Fiber Optics and Optical Communications
Phase Recovery Algorithm for Adaptive Probabilistic Shaping Signal Based on K-means
Xiongwei Yang, Feng Zhao, Linxian Zhao, and Zhao Meng
A self-adaptive phase recovery algorithm based on K-means clustering is proposed to solve the problem of self-adaptive phase recovery of unknown probability shaping factor signals. Through theoretical analysis and numerical simulation, the feasibility of constellation point modulus radius repositioning based on K-meansA self-adaptive phase recovery algorithm based on K-means clustering is proposed to solve the problem of self-adaptive phase recovery of unknown probability shaping factor signals. Through theoretical analysis and numerical simulation, the feasibility of constellation point modulus radius repositioning based on K-means clustering is verified. Then, the K-means clustering is combined with the feedforward carrier phase recovery algorithm to solve the problem of relative amplification of constellation points after normalization of probabilistic shaped signals, and the adaptive recovery of signal phase of unknown probability shaping factor is realized. The 16 quadrature amplitude modulation (QAM) and 64QAM signals at different optical signal-to-noise ratio (OSNR) and laser linewidth are simulated. The results show that the proposed algorithm can be used not only for phase recovery of signals with unknown probability shaping factor, but also for phase recovery of uniform QAM signals. Because the proposed algorithm considers the influence of noise in the repositioning of the constellation point modulus, higher precision phase compensation can be realized under the same number of test phases. The algorithm improves the tolerance of OSNR by about 1 dB for uniform QAM signals..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0906001 (2022)
Phase Demodulation Method for Non-Periodic Signal in Extrinsic Fabry-Perot Interferometric Sensor
Shuhuan Zhang, and Yi Jiang
A three-wavelength quadrature phase compensation method for recovering non-periodic dynamic signals in an extrinsic Fabry-Perot interferometric (EFPI) sensor is proposed. The influence of the direct-current component is eliminated by using three interferometric signals, and two orthogonal signals are generated by the pA three-wavelength quadrature phase compensation method for recovering non-periodic dynamic signals in an extrinsic Fabry-Perot interferometric (EFPI) sensor is proposed. The influence of the direct-current component is eliminated by using three interferometric signals, and two orthogonal signals are generated by the phase compensation algorithm to demodulate the signals to be tested. In the experiment, an aperiodic dynamic signal is loaded on the EFPI sensor, and three laser interferometric methods are used to demodulate the experimental data. The results show that the proposed method has higher demodulation accuracy, and is suitable for the high temperature environment with cavity length change and the measurement of non-periodic dynamic signals..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0906002 (2022)
Geometric Optics
High-Temperature Material Spectral Emissivity Measurement Technology Based on 800 mm Semi-Ellipsoidal Reflector
Yongxing Yang, Xinrui Wang, Beibei Chen, Hengrui Guan... and Jinbiao Zhao|Show fewer author(s)
To solve the problem of material emissivity measurement at medium-high temperature, a high-temperature material spectral emissivity measurement technology based on semi-ellipsoidal reflector is proposed. In this technology, a 800 mm semi-ellipsoidal mirror is used to focus the signal light in a large range, three kindsTo solve the problem of material emissivity measurement at medium-high temperature, a high-temperature material spectral emissivity measurement technology based on semi-ellipsoidal reflector is proposed. In this technology, a 800 mm semi-ellipsoidal mirror is used to focus the signal light in a large range, three kinds of off-axis parabolic mirrors are used to switch different test fields of view, and the sample is heated by a high-power laser. The measurement error of the designed system is studied in simulation. The results show that the maximum measurement deviation of reflectivity is 0.035, and that of transmittance is 0.031. An emissivity measurement system based on a 800 mm semi-ellipsoidal mirror is constructed. Then, the reflectivity, transmittance, and emissivity of an alloy material and a translucent material are measured, which shows that the designed system can realize the measurement from normal temperature to medium-high temperature (300--1200 K), multi-field of view (30°, 60°, 90°), and wide spectrum (2--14 μm)..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0908001 (2022)
Imaging Systems
Terahertz Light Field Imaging Occlusion Removing Algorithm Based on Multi-Perspective Synthetic Aperture
Moxuan Yang, Yuanmeng Zhao, Fengxia Zhu, Hongfei Zhang... and Cunlin Zhang|Show fewer author(s)
In order to solve the problem that the acquisition of interesting information is affected by foreground occlusion in terahertz field imaging, a terahertz light field imaging occlusion culling algorithm based on multi-perspective synthetic aperture is proposed. Based on the analysis of digital refocusing principle of teIn order to solve the problem that the acquisition of interesting information is affected by foreground occlusion in terahertz field imaging, a terahertz light field imaging occlusion culling algorithm based on multi-perspective synthetic aperture is proposed. Based on the analysis of digital refocusing principle of terahertz light field imaging, the original data of the terahertz light field is collected by using a terahertz focal plane array camera, and the depth of digital refocusing is located by determining the minimum generalization error. Finally, the reconstructed image is enhanced by using empirical mode decomposition (EMD) method. The terahertz image of the object with clear contour and interference suppression is obtained. The experimental results show that the combination of terahertz light field technology and synthetic aperture technology can effectively reduce the influence of occlusion, and it is proved that EMD method has the ability to improve the quality of terahertz image..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0911001 (2022)
Thermal Imaging Detection Method of Leak Gas Clouds Based on Support Vector Machine
Jing Weng, Pan Yuan, Minghe Wang, Li Li... and Bingcai Sun|Show fewer author(s)
Gas leak detection technology based on thermal imaging has become an important means of oil and gas leakage detection because of its high detection efficiency and visibility. The conventional methods need personnel’s subjective judge to trace gases from the video, so it is easy to lead miss and false detection. TherefoGas leak detection technology based on thermal imaging has become an important means of oil and gas leakage detection because of its high detection efficiency and visibility. The conventional methods need personnel’s subjective judge to trace gases from the video, so it is easy to lead miss and false detection. Therefore, this paper studies a thermal imaging detection algorithm of leaking gas clouds based on scale invariant feature transform (SIFT) and support vector machine (SVM), and uses the inter-frame difference method to screen the target region from the infrared image sequence. SIFT features of leaking gas and disturbance were extracted, respectively. SVM is used to identify the target in the candidate region and extract the leaking gas cloud. A database of 1000 typical target images was established for real complex scenes, including ethylene, methane, and other gas leakage images and disturbing images such as moving person, trees, and weeds. Through detection experiment, the classification accuracy of the proposed method for leaking gas clouds at 10--150 m can reach 92.5%. The results show that this detection method can automatically eliminate the interference of other moving objects and effectively detect the leaking gas cloud..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0911002 (2022)
Instrumentation, Measurement and Metrology
White Light Interferometry Stitching Measurement of Gull-Wing Aspheric Optics
Wenwen Lu, Jingyang Guo, and Shanyong Chen
In order to solve the problem of gull-wing aspheric profile detection, a white light interferometry stitching measurement scheme is proposed. The scanning path is planned by combining white light micro-interferometry with the measurement principle of subaperture stitching. The white light interferometry stitching measuIn order to solve the problem of gull-wing aspheric profile detection, a white light interferometry stitching measurement scheme is proposed. The scanning path is planned by combining white light micro-interferometry with the measurement principle of subaperture stitching. The white light interferometry stitching measurement platform is constructed, and the high-precision measurement of 59 subapertures of a 10 mm gull-wing aspheric surface is completed. The measured subaperture data are stitched by using the synchronous subaperture stitching algorithm, and the full-aperture profile error is obtained. The comparative experiments on the detection of gull-wing aspheric surface by using high-precision profiler and computer generated hologram (CGH) compensator are carried out. The results show that the profile error and distribution of the proposed detection scheme are consistent with those obtained by high-precision profiler and CGH compensator, which effectively verifies the correctness of the proposed measurement scheme..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0912001 (2022)
Scratch Evolution for Monocrystalline Silicon During Chemical-Mechanical Polishing
Jingjing Xia, Jun Yu, Zhanshan Wang, and Siwen Lu
Chemical-mechanical polishing is a commonly adopted technique for the fabrication of super-smooth monocrystalline silicon mirror. Rogue particles during chemical-mechanical polishing process always result in scratches on mirror surface hence reduce surface quality. To systematically study the relationship between impurChemical-mechanical polishing is a commonly adopted technique for the fabrication of super-smooth monocrystalline silicon mirror. Rogue particles during chemical-mechanical polishing process always result in scratches on mirror surface hence reduce surface quality. To systematically study the relationship between impurities in polishing slurry and plastic scratches on monocrystalline silicon surface with different crystal orientations, experiments on polishing Si(111), Si(110) and Si(100) surface by using diamond doped polishing slurries are designed. Scratch morphologies under different crystal orientations and different doping concentrations are measured by profilometer, and evaluated by calculating scratch width distribution, scratch depth distribution, roughness degree, surface roughness and two-dimensional power spectral density after load normalization. Results show that the size of rogue particles in the polishing slurry and the width of scratches on silicon surface obey the normal distribution. With the increase of rogue particle concentration, the scratch morphology changes from non-periodic characteristics to periodic fluctuations, and the roughness shows a jump point. In addition, in the case of the same diamond doping concentration, Si(110) has better tolerance of rogue particles at the initial stage of scratch generation..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0912002 (2022)
Temperature Inversion Algorithm for Multi-Spectral Measurement of Material Shock Radiation Characteristics
Ningchao Zhang, Fan Yang, Juan Ren, Yuetao Du... and Fusheng Liu|Show fewer author(s)
The shock radiation temperature of materials is an important physical parameter for the study of equation of state under the action of high temperature and high pressure, which is of great significance to weapon development, scientific research, and industrial manufacturing. Aiming at the characteristics of instantaneoThe shock radiation temperature of materials is an important physical parameter for the study of equation of state under the action of high temperature and high pressure, which is of great significance to weapon development, scientific research, and industrial manufacturing. Aiming at the characteristics of instantaneous non-contact, complex measurement environmental noise, and unmeasurable emissivity inverted by temperature, a new temperature inversion method is designed to improve the accuracy of temperature acquisition. According to the constrained optimization theory, the multiplier penalty function method and particle swarm optimization (PSO) algorithm are combined to realize the series of the two models, and the PSO-multiplier penalty function algorithm is improved. The results show that the hybrid model solving method fully combines the advantages of the two single algorithms and improves the temperature inversion accuracy and operation efficiency of the test data of impact radiation. It provides a guarantee for studying the real temperature of material under impact radiation..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0912003 (2022)
Misalignment Error Analysis of Segmented Diffractive Telescope
Chencheng Li, Lihua Wang, Fengtao Yan, and Bin Fan
The misalignment error of the spliced diffraction telescope has an important influence on the imaging quality of the optical system. Therefore, the tolerance of the misalignment error of the spliced Fresnel lens is analyzed, and the theoretical calculation formula of the misalignment error based on Rayleigh criterion iThe misalignment error of the spliced diffraction telescope has an important influence on the imaging quality of the optical system. Therefore, the tolerance of the misalignment error of the spliced Fresnel lens is analyzed, and the theoretical calculation formula of the misalignment error based on Rayleigh criterion is derived. The tolerance of the optical system including the spliced primary mirror and achromatic optical path with an aperture of 1.5 m is analyzed. The simulation results show that the wavefront aberrations within the tolerance range meet the Rayleigh criterion and Streyer ratio, so the tolerance analysis can provide effective theoretical guidance for the installation, adjustment and detection of diffraction telescopes..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0912004 (2022)
Phase Unwrapping Algorithm for Structured Light Based on Fringe-Order Encoding and Modulation
Jie Li, Bin Chen, Xinyi Zeng, and Shiqian Wu
This paper first uses the phase-order encoding and modulation methods to superimpose the phase-order information into the phase-shifting image, and then proposes a method to directly use the phase-shifting image to unwrap the phase. On the projection side, this paper firstly proposes an adjacent non-repetitive De BruijThis paper first uses the phase-order encoding and modulation methods to superimpose the phase-order information into the phase-shifting image, and then proposes a method to directly use the phase-shifting image to unwrap the phase. On the projection side, this paper firstly proposes an adjacent non-repetitive De Bruijn sequence, uses this sequence to encode the phase order, and then modulates and superimposes the periodic order code sequence into the multi-step phase shift image. Correspondingly, in the decoding stage, this paper demodulates and decomposes the wrapped phase and period order coding sequence from the captured phase-shifting image at the same time, then restores the true period order information through sequence matching, and finally unwraps the absolute phase accurately. We take the four-step phase shifting method as an example. Compared with the traditional temporal phase unwrapping algorithm, the method in this paper reduces the number of projection images from 10 (64 phase periods) to 4, which improves the measurement efficiency..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0912005 (2022)
Nano-Opto-Electromechanical Magnetic Vector Sensor Design Based on Black Phosphorus
Wenyao Liu, Chenxi Liu, Wei Li, Enbo Xing... and Jun Liu|Show fewer author(s)
Nanomechanical resonant sensors based on two-dimensional materials have great potential in sensing with the advantages of small size, high frequency, and high-quality factor. Among them, black phosphorus provides a unique opportunity for in-plane vector sensing due to its corrugated planar structure and anisotropic mecNanomechanical resonant sensors based on two-dimensional materials have great potential in sensing with the advantages of small size, high frequency, and high-quality factor. Among them, black phosphorus provides a unique opportunity for in-plane vector sensing due to its corrugated planar structure and anisotropic mechanical characteristics. In this paper, a new type of a nano-opto-electromechanical magnetic vector sensor based on optically excited optical readout is designed using black phosphorus. Using the finite element analysis method, the influences of the number of layers and the length-width ratio of black phosphorus on the vector property are studied, and the system structure is optimized with the size of 0.6 μm×0.134 μm×0.5 nm. The anisotropy of the response to the magnetic field in the directions of high Young’s modulus and low Young’s modulus is explored, respectively. By using the spatial distribution of resonant modes, the influences of the angle and length-width ratio on the sensitivity and vector property of the device are explained. It can be found that in the Armchair direction, when the magnetic field rotates 90°, the sensitivity changes from -4.048 MHz/mT to 5.796 MHz/mT. Compared with Lorentz force-based micro-electromechanical sensors, the resonant frequency of the designed sensor can be improved by 6 orders of magnitude, and its size can be reduced by 6 orders of magnitude. This design provides a new method for the preparation of a nano-opto-electromechanical vector sensor..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0912006 (2022)
Integrated Optics
On-Chip Terahertz Demultiplexer and Grating Coupler Based on Reverse Design
Guofeng Zhu, Zhenrong Dai, Xuewei Ju, Shuncong Zhong... and Feng Huang|Show fewer author(s)
The traditional construction methods of terahertz demultiplexers and grating couplers need to be calculated with the help of classical theory and experience, so their design flow is complex, and their performance depends on the unit structure parameters. With the proposal and application of reverse design method, the dThe traditional construction methods of terahertz demultiplexers and grating couplers need to be calculated with the help of classical theory and experience, so their design flow is complex, and their performance depends on the unit structure parameters. With the proposal and application of reverse design method, the device structure that meets the functional requirements can be designed on a limited size substrate. Based on this, the reverse design method is applied to the design of terahertz demultiplexer and grating coupler with dimensions of 3 mm×3 mm×200 μm and 12 mm×12 mm×200 μm, respectively. The simulation results of finite-difference time-Ddomain (FDTD) show that the terahertz demultiplexer can perfectly separate a beam of terahertz waves with two frequencies from two ports, and the transmittance is more than 0.75 at 0.500 THz and 0.417 THz, and the crosstalk between adjacent channels is less than -19 dB. The coupling efficiency of the terahertz grating coupler is as high as 0.85 at 0.32 THz..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0913001 (2022)
Lasers and Laser Optics
Experimental Exploration of Er∶YAG Cascaded Pulsed Laser at Room Temperature
Sibo Wang, Ye Tian, Bo Qu, Zhanda Zhu... and Qiang Li|Show fewer author(s)
Cascaded mid-infrared (MIR) Er∶YAG pulsed lasers at room temperature are reported. The characteristic wavelength of the cascaded emission is experimentally observed to be 1469 nm, and that of the excited-state absorption is determined as 1676 nm. Er∶YAG crystals with doping concentrations (atomic number fractions) of 7Cascaded mid-infrared (MIR) Er∶YAG pulsed lasers at room temperature are reported. The characteristic wavelength of the cascaded emission is experimentally observed to be 1469 nm, and that of the excited-state absorption is determined as 1676 nm. Er∶YAG crystals with doping concentrations (atomic number fractions) of 7.5% and 10% are adopted to compare the MIR output energy under the cascade and non-cascade conditions. For the Er∶YAG with a doping concentration of 7.5%, the maximum single pulse energy of MIR laser increases from 0.62 mJ (non-cascade) to 0.99 mJ (cascade), increasing by about 59.7%, and for Er∶YAG with a doping concentration of 10%, that increases from 1.04 mJ (non-cascade) to 1.51 mJ (cascade), increasing by about 45.2%. The experimental results confirm the existence of cascade output at room temperature in low-doped Er∶YAG crystals. The cascade is helpful to improve the single pulse energy of the mid-infrared laser..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0914001 (2022)
Theoretical and Experimental Research on 100 kHz Cavity-Dumped Thin-Disk Laser
Jing Dong, Hantian Chen, Hailin Wang, Guangzhi Zhu... and Xiao Zhu|Show fewer author(s)
In this article, we carried out theoretical and experimental studies on the output characteristics of a cavity-dumped thin-disk laser operating at 100 kHz. Firstly, a theoretical model of the rate equation of the cavity-dumped thin-disk laser was established. The model considered the number of spontaneous emission photIn this article, we carried out theoretical and experimental studies on the output characteristics of a cavity-dumped thin-disk laser operating at 100 kHz. Firstly, a theoretical model of the rate equation of the cavity-dumped thin-disk laser was established. The model considered the number of spontaneous emission photons newly added in the resonant cavity per unit time, and the ratio of the number of spontaneous emission photons to the total number of spontaneous emission photons was analyzed. And then we performed simulations based on some parameters. Next, we built a cavity-dumped thin-disk laser with a repetition rate of 100 kHz, and the average power of nanosecond laser pulse output was 253 W. The optical-optical efficiency was about 35.2%, the pulse width was 10.4 ns, and the single pulse energy was 2.53 mJ. The peak power exceeded 200 kW, and the optical quality M2 in the x and y directions was 9.77 and 9.27, respectively. For the dynamic stability of the cavity-dumped Q-switching, the influence of Pockels cell gate time on the output power and stability of the output pulse was further studied. In the experiment, the phenomenon of period doubling bifurcation and deterministic chaos were observed. The simulation results are consistent with the experimental results..
Acta Optica Sinica
- Publication Date: May. 20, 2022
- Vol. 42, Issue 9, 0914002 (2022)
Machine Vision
Polarization Imaging Detection of Individual Camouflage Based on Two-Stream Fusion Network
Rongchang Wang, Feng Wang, Shuaijun Ren, and Yong Wang
There is a high degree of color similarity between the individual camouflage target and the background, the target has a highly complex posture, and there are occlusion problems, which make individual camouflage target detection more challenging than traditional target detection. In order to solve the above problems, aThere is a high degree of color similarity between the individual camouflage target and the background, the target has a highly complex posture, and there are occlusion problems, which make individual camouflage target detection more challenging than traditional target detection. In order to solve the above problems, a depth learning algorithm based on polarization information and RGB (Red,Green,Blue) information is proposed, and the polarization image dataset CIP3K (Multicam type camouflage dataset and Woodland type camouflage dataset) is constructed. Based on Faster R-CNN (Faster Region-Convolutional Neural Network), a dual-stream feature fusion network TSF-Net is proposed, which can integrate target polarization feature information and RGB feature information. A large number of experiments are carried out on the CIP3K dataset to test the performance of the TSF-Net model and other detection models. The experimental results show that, compared with Faster R-CNN, the average detection accuracy of the TSF-Net model on the two datasets is increased by 8.2 percentages and 8.8 percentages, respectively, and is better than some mainstream object detection models..
Acta Optica Sinica
- Publication Date: May. 20, 2022
- Vol. 42, Issue 9, 0915001 (2022)
Materials
FDTD Simulation and Study on Effect of Metal Nanoparticle Introduction on Light Extraction of Top-Emitting OLED
Saihu Pan, hang Yu, Yunping Zhao, Suhao Hu... and Bin Wei|Show fewer author(s)
Some photons will be transformed into surface plasmon polaritons and dissipated along the metal surface due to the existence of the interface between metal cathode and organic layer in organic light-emitting diode (OLED). At the same time, the metal cathode absorbs part of the light energy. Both of these cases will resSome photons will be transformed into surface plasmon polaritons and dissipated along the metal surface due to the existence of the interface between metal cathode and organic layer in organic light-emitting diode (OLED). At the same time, the metal cathode absorbs part of the light energy. Both of these cases will result in a very low power efficiency of the device. The changes of luminous efficiency of the device with the structure of Ag (100 nm)/MoO3 (5 nm)/NPB (35 nm)/EML (20 nm)/Alq3 (40 nm)/Al (20 nm)/MoO3 (50 nm) are analyzed after the introduction of silver nanoparticles (Ag NPs) or gold nanoparticles (Au NPs). Furthermore, the positions of the metal nanoparticles are changed to observe the effect of different positions of the nanoparticles on the luminous efficiency of the device. The finite-difference time-domain method is used to simulate the luminous efficiencies of devices without metal nanoparticles and metal nanoparticles at different positions of the device. The results show that both Ag NPs and Au NPs can improve the luminous efficiency, and Ag NPs are better than Au NPs. At the wavelength of 468 nm, when Ag NPs are located on the surface of Al cathode, the middle of electron transport layer (ETL) and the Ag surface, the transmittance of the device is 51.1%, 50.5% and 45.5%, respectively. However, the transmittance of the reference device without Ag NPs is only 43.3%..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0916001 (2022)
Nonlinear Optics
Influencing Factors of Temporal Modes of Raman Photons in Long Optical Fibers
Nannan Liu, Zhenming Dou, Ruoyi Jia, Yu Zhao... and Fengxiao Zhai|Show fewer author(s)
Under the influence of loss, dispersion, and self-phase modulation, the second-order correlation function of spontaneous Raman scattering photon is calculated by piecewise analysis, and the time mode characteristics of spontaneous Raman scattering pumped by pulsed light in long optical fiber are studied. The results shUnder the influence of loss, dispersion, and self-phase modulation, the second-order correlation function of spontaneous Raman scattering photon is calculated by piecewise analysis, and the time mode characteristics of spontaneous Raman scattering pumped by pulsed light in long optical fiber are studied. The results show that in the case of no dispersion and self-phase modulation, the second-order correlation function of spontaneous Raman scattering photon is not affected by pump loss, but is only determined by the ratio of pump pulse width to Raman photon coherence time. It has the same expression as the second-order correlation function of spontaneous parametric downconversion photons. In the case of dispersion and self-phase modulation, the change of pump pulse width caused by dispersion and self-phase modulation and the dispersion-induced temporal wall-off between pump light and Raman photons change the time mode of Raman photons. The second-order correlation function of spontaneous Raman scattering photons depends on the fiber loss coefficient, dispersion parameters and initial pump pulse width, which is no longer the same as that of spontaneous parametric down conversion photons..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0919001 (2022)
Optical Design and Fabrication
Optimization Design Method of Freeform Reflector for Direct Solar Radiation Measurement
Xiaotong Yang, Guoyu Zhang, Jian Zhang, Wei Chong... and Zhengjie Niu|Show fewer author(s)
This paper proposed an optimization design method of freeform reflectors for direct solar radiation measurement to solve the key problem that year-round measurement uniformity is difficult to guarantee due to the tracking device used in the process of direct solar radiation measurement and to achieve tracking-free fullThis paper proposed an optimization design method of freeform reflectors for direct solar radiation measurement to solve the key problem that year-round measurement uniformity is difficult to guarantee due to the tracking device used in the process of direct solar radiation measurement and to achieve tracking-free full-season and full-latitude uniform measurement of direct solar radiation. The global variation law of the direct solar radiation angle was analyzed, and the initial structure model of a freeform reflector was built. An evaluation function of the radiative flux uniformity at spatiotemporal scales (RFUS) was constructed, a dichotomous evolution mechanism and a variable length mechanism without a remainder were developed, and an optimization method of freeform reflectors based on the evolutionary strategy was proposed. For the purpose of achieving full-latitude uniform measurement of direct solar radiation around the world, four representative freeform reflectors with chromosome subdivision parameters of 3°, 1°, 0.5°, and 0.25°, respectively, were iteratively optimized and simulated. The results show that the RFUS is the best, 92.36% to be exact, when the chromosome subdivision parameter is 0.25°. Finally, tests were set up to verify the position of the reflection spot center and the RFUS. According to the results, the maximum linear distance of the spot center obtained by this method is about 1.5 mm, and RFUS is 90.34%. The proposed method can be used to achieve full-spatiotemporal uniform measurement of direct solar radiation, and it provides a theoretical basis and technical support for new products and applications in the field of solar radiation measurement..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0922001 (2022)
360° Floating Display System Based on Human Eye Tracking and Its Distortion Correction Method
Dingtian Xu, Haifeng Li, and Liang Xu
The traditional flat-panel display technology cannot satisfy the display effect of 360° viewing angle and high resolution. A 360° floating display system based on human eye tracking is proposed. The multi-camera eye tracking algorithm is used to obtain the observer viewpoint position in real time, and the corThe traditional flat-panel display technology cannot satisfy the display effect of 360° viewing angle and high resolution. A 360° floating display system based on human eye tracking is proposed. The multi-camera eye tracking algorithm is used to obtain the observer viewpoint position in real time, and the corresponding view angle picture is generated by OpenGL. In order to realize 360° display, a catadioptric cylindrical projection optical system is designed. In order to make full use of the limited resolution of the projector, a half-circle display scheme is proposed. In order to display the correct image, a predistortion correction method based on Bezier surface and a polar coordinate system conversion method are proposed, and the 360° horizontal viewing angle and vertical viewing angle with a certain range of the system are finally realized. The experimental results show that the proposed system can achieve static or dynamic floating display effects with high resolution and low cost..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0922002 (2022)
Ion Beam Polishing Process of Off-Axis Parabolic Mirror
Guobin Sun, Shilei Jiang, Yuhao Zhang, and Jin Zhang
Aiming at the problems of thermal effect accumulation and iterative processing efficiency in the process of off-axis parabolic mirror ion beam modification, a method is proposed to combine batch machining with variable beam diameter machining, which divided the total removal amount according to a certain proportion, anAim
ing at the problems of thermal effect accumulation and iterative processing efficiency in the process of off-axis parabolic mirror ion beam modification, a method is proposed to combine batch machining with variable beam diameter machining, which divided the total removal amount according to a certain proportion, and the experimental exploration is carried out by using this method. The spherical mirrors with an aperture of 110 mm, a radius of curvature of 1732.7 mm, an initial surface peak-valley value (PV) of 0.525λ (λ=632.8 nm) and a root mean square (RMS) value of 0.025λ are polished in batches. The off-axis parabolic mirrors with vertex radius of curvature of 1728 mm, off-axis of 85 mm, PV of 0.36λ and RMS of 0.029λ are obtained. Based on the analysis of the experimental process and results, it is proved that the batch machining method can effectively eliminate the thermal effect in the ion beam machining process, and the local finishing method with variable beam diameter can reduce the number of iterative machining and improve the machining efficiency.
.Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0922003 (2022)
Optical Devices
Broadband Terahertz Absorber Based on Graphene Metamaterial
Limin Ma, Han Xu, Yuhuang Liu, Guili Xu, and Wanlin Guo
In order to expand the relative absorption bandwidth of terahertz absorber, an ultra-thin, wide-band, and tunable terahertz absorber based on graphene metamaterial is designed, which is composed of patterned graphene layer, dielectric layer, and metal reflection substrate. The simulation results show that the absorptivIn order to expand the relative absorption bandwidth of terahertz absorber, an ultra-thin, wide-band, and tunable terahertz absorber based on graphene metamaterial is designed, which is composed of patterned graphene layer, dielectric layer, and metal reflection substrate. The simulation results show that the absorptivity of the absorber at 4.48 THz frequency is 99.98%, and the absorptivity at this frequency can be changed to 25.08% by adjusting the chemical potential of graphene. At the same time, the absorber shows the absorption characteristic of insensitive to the polarization of incident wave, and can still maintain a certain wide-band absorption characteristic when the terahertz wave is tilted. On this basis, a terahertz absorber based on three-layer patterned graphene is designed, which can further expand the absorption bandwidth. The simulation results show that the absorption rate of the absorber is higher than 90%, and the relative absorption bandwidth is 97% between 1.90 THz and 5.49 THz..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0923001 (2022)
Reviews
Progress and Prospect of Mid-Infrared Fiber Laser Technology
Yulong Cui, Zhiyue Zhou, Wei Huang, Zhixian Li... and Zefeng Wang|Show fewer author(s)
Mid-infrared laser has important application value in many fields, such as communication, remote sensing, security inspection, optoelectronic countermeasures, and so on, and has always attracted enormous attention. There are many methods for generation of mid-infrared laser, among which mid-infrared fiber lasers have tMid-infrared laser has important application value in many fields, such as communication, remote sensing, security inspection, optoelectronic countermeasures, and so on, and has always attracted enormous attention. There are many methods for generation of mid-infrared laser, among which mid-infrared fiber lasers have the characteristics of compact structure, good beam quality, and high conversion efficiency, and so on, so they are considered as the most promising way to achieve portable, stable, efficient, and high-power mid-infrared laser emission. With the improvement of manufacturing technology of soft glass fibers, mid-infrared fiber laser technologies have achieved rapid development, and the output power level has also been greatly enhanced. However, limited by the types of rare earth ions, the fabrication process and chemical stability of soft glass fibers, the mid-infrared lasers based on soft glass fibers have technical difficulties in further improving the power and expanding the wavelength. The mid-infrared fiber gas lasers appeared in recent years provide an effective solution to these problems. The research status of mid-infrared fiber laser technologies are reviewed in detail, including the new mid-infrared fiber lasers based on gas-filled hollow-core fibers, and the development trend of mid-infrared fiber laser technologies is briefly prospected..
Acta Optica Sinica
- Publication Date: May. 20, 2022
- Vol. 42, Issue 9, 0900001 (2022)
Spectroscopy
Characteristics of Step Surface Shape Error in Snapshot Interference Imaging Spectrometer
Jinguang Lü, Jingqiu Liang, Weibiao Wang, Yuxin Qin, and Jin Tao
Through coupling the light fields of multiple imaging with a microlens array and phase modulation with multiple micro-mirrors, the snapshot interference imaging spectrometer achieves the simultaneous detection of the image and spectrum of a dynamic scene. The substrate processing accuracy and film surface stress cause Through coupling the light fields of multiple imaging with a microlens array and phase modulation with multiple micro-mirrors, the snapshot interference imaging spectrometer achieves the simultaneous detection of the image and spectrum of a dynamic scene. The substrate processing accuracy and film surface stress cause the bending deformation of the step surfaces in the multiple micro-mirrors and further affect the quality of the spectrum and imaging. In this paper, the surface shape error characteristics of bending deformation of the step surfaces in the multiple micro-mirrors were analyzed to build a light field transmission model of the step surface shape error. The calculation results show that different distributions of the step surface shape error produce different intensity changes in the interference image point array in each field of view and different noise distribution characteristics in the recovered spectrum. The step surface shape error introduces a phase error into the recovered spectrum in different imaging fields and modulates the intensity distribution of coherent image points. The reconstructed spectrum error increases monotonically with the absolute value of the step sagittal height of the two multiple micro-mirrors. This relationship can be leveraged to evaluate system performance with the measured value of the step sagittal height and provide theoretical guidance for device fabrication..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0930001 (2022)
Spectral Calibration and Matching Method for Ultraviolet-Visible Polarization Imaging Spectrometer
Jingjing Shi, Mengfan Li, Yadong Hu, Gaojun Chi... and Jin Hong|Show fewer author(s)
The dispersion effect of the Wollaston prism in the ultraviolet-visible polarization imaging spectrometer causes the center coordinates of the same spatial channel of the detector to shift and ultimately affects the accuracy of target signal detection. According to the polarization demodulation algorithm, spectral matcThe dispersion effect of the Wollaston prism in the ultraviolet-visible polarization imaging spectrometer causes the center coordinates of the same spatial channel of the detector to shift and ultimately affects the accuracy of target signal detection. According to the polarization demodulation algorithm, spectral matching is also required when the modulation spectra of the two orthogonal components (S spectrum and P spectrum) exiting from the Wollaston prism are used to demodulate polarization information. In response, this paper proposes a spectral calibration and matching method. To start with, parallel light sources are used to calibrate the corresponding relationship between the field-of-view angle of the instrument and the pixel in the spatial dimension, and pixel coordinate collections corresponding to each spatial channel are extracted to determine a field-of-view calibration equation. Subsequently, in the same spatial channel, the corresponding relationship between wavelength and pixel is calibrated by the standard light source of a low-pressure mercury lamp to obtain a spectral calibration equation. Then, the results of field-of-view calibration and spectral calibration are utilized to match the orthogonal component spectra. Finally, the calibration results are tested on the characteristic wavelength of the Fraunhofer line in the solar spectra. The results show that the positions of the spectral absorption peaks of the two orthogonal components exiting from the ultraviolet-visible polarization imaging spectrometer have favorable consistency. Specifically, the deviation between the calibration value and the standard one is within 0.1 nm, which verifies the accuracy of the calibration results..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0930002 (2022)
Quantitative Analysis of Carbon Content in Fly Ash Using LIBS Based on Support Vector Machine Regression
Peng Chen, Chao Qi, Renwei Liu, Zhenzhen Wang... and Yoshihiro Deguchi|Show fewer author(s)
Laser induced breakdown spectroscopy (LIBS) is used to analyze the prepared fly ash samples, and support vector machine regression (SVR) model is used to predict the carbon content of fly ash. The structure parameters of radial basis function (RBF) kernel function and polynomial function are optimized by grid search meLaser induced breakdown spectroscopy (LIBS) is used to analyze the prepared fly ash samples, and support vector machine regression (SVR) model is used to predict the carbon content of fly ash. The structure parameters of radial basis function (RBF) kernel function and polynomial function are optimized by grid search method, and then SVR models based on internal standard element characteristic spectrum, full spectrum, and main element characteristic spectrum are established respectively. The research shows that SVR model of RBF and polynomial kernel function can achieve the same analysis accuracy under ideal structural parameters, but RBF can complete the model optimization quickly and is not easy to underfit. The analysis accuracy of the SVR model based on the characteristic spectrum of internal standard elements is similar to that of the internal standard method, and the SVR model based on full spectrum shows obvious overfitting phenomenon. The regression coefficient of the SVR model based on the characteristic spectrum of the main elements is 0.986, the root mean square error of correction is 1.79%, and the root mean square error of prediction is 2.57%, indicating that the model can effectively avoid underfitting and overfitting..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0930003 (2022)
LED Spectral Matching Based on Adaptive Differential Evolution Algorithm
Zhen Cheng, Ganshang Si, Zhengang Li, Zhiqiang Ning... and Yonghua Fang|Show fewer author(s)
An adaptive differential evolution algorithm is proposed as a spectral matching algorithm to synthesize various target spectra with monochromatic light-emitting diodes (LEDs). The gaussian correction model is used to characterize the distribution of monochromatic LEDs. The standard AM1.5 solar spectrum and vegetation sAn adaptive differential evolution algorithm is proposed as a spectral matching algorithm to synthesize various target spectra with monochromatic light-emitting diodes (LEDs). The gaussian correction model is used to characterize the distribution of monochromatic LEDs. The standard AM1.5 solar spectrum and vegetation spectrum are simulated based on equally distributed LEDs,and the correlation coefficient and root-mean-square error are used as evaluation criteria. On this basis, the LEDs in the laboratory are used for experimental verification, and the fitting effect of the proposed algorithm is better than the simulated annealing algorithm and the genetic algorithm. The experimental results show that the proposed adaptive differential evolution algorithm, with automatic setting of parameters and good fitting effect, can be widely used in the LED spectral matching simulation tests and engineering practices..
Acta Optica Sinica
- Publication Date: May. 05, 2022
- Vol. 42, Issue 9, 0930004 (2022)
X-Ray Optics
Simulation and Test of Effective Area of Lobster Eye X-Ray Optical Device
Longhui Li, Yan Gu, Zhen Zhang, Zhao Xu... and Jianqiang Liu|Show fewer author(s)
Lobster eye X-ray focusing telescope is one of the important equipment for X-ray space astronomical observation in the future. This equipment will become a powerful tool to study the Earth’s space environment under various solar wind conditions. Aiming at the design and simulation of the effective area of lobster eye XLobster eye X-ray focusing telescope is one of the important equipment for X-ray space astronomical observation in the future. This equipment will become a powerful tool to study the Earth’s space environment under various solar wind conditions. Aiming at the design and simulation of the effective area of lobster eye X-ray microporous optical devices, the relationship between structural parameters and geometric collection area is studied, and the effects of different film materials and surface roughness on X-ray reflectivity are calculated based on Fresnel formula. The performance test of effective area X-ray is completed by using X-ray beam test equipment and single-photon acquisition mode. The results show that the effective area of lobster eye optics is mainly determined by the material of the film and the roughness of the inner wall. At the same time, the effective area of Ir film can be increased from 2.15 cm 2 to 2.47 cm 2 when the energy is 1 keV..
Acta Optica Sinica
- Publication Date: May. 20, 2022
- Vol. 42, Issue 9, 0934001 (2022)
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