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Atmospheric Optics and Oceanic Optics|248 Article(s)
Neural Network Inversion Method for Atmospheric Temperature and Relative Humidity Profiles Based on FY-3E/HIRAS
Yike Zou, Ying Wu, Jingwen Ma, Yuanyuan Huang... and Qijia Fu|Show fewer author(s)
Using the observations made by the hyperspectral infrared atmospheric sounder (HIRAS) carried on the FY-3E polar orbiting meteorological satellite, the back propagation neural network (BPNN) method is employed to conduct research on the inversion of atmospheric temperature and relative humidity vertical profiles in the East China region. An atmospheric temperature and humidity inversion model is constructed, and the parameters are optimized to obtain a network model configuration with high inversion accuracy, resulting in all-weather, high-precision atmospheric temperature and relative humidity profile. According to the results, the following conclusions can be drawn. 1) Temperature inversion results of the model have a mean error (ME) between -1.00 K and 1.00 K at each pressure layer, except that the absolute value of ME in the lower layer of the cloudy sky is greater than 1.00 K. The validation experiment conducts on ERA5 data has root mean square error (RMSE) between 0 K and 2.00 K for most pressure layers, except for ~2.50 K at the 925?950 hPa layer, the minimum RMSE corresponds to the 200?500 hPa, indicating higher temperature inversion accuracy in the upper atmosphere. 2) For the inversion of atmospheric relative humidity, the ME of the lower and upper atmosphere is larger, whereas that of the middle atmosphere is smaller; RMSE is larger in the middle layers and smaller in the lower and upper layers. 3) Compared to clear sky condition, the accuracy of temperature and relative humidity inversion models under cloudy sky condition is slightly lower. 4) The deviation of the temperature and relative humidity inversion results from the sounding data is slightly greater than the deviation from the ERA5 data although the trend of error with height variation is similar. The HIRAS data generally performs well in inverting the temperature and relative humidity of clear and cloudy skies, with high inversion accuracy. Therefore, this study has important reference value for inversion methods and techniques of atmospheric temperature and relative humidity, providing useful insights for future related research. Using the observations made by the hyperspectral infrared atmospheric sounder (HIRAS) carried on the FY-3E polar orbiting meteorological satellite, the back propagation neural network (BPNN) method is employed to conduct research on the inversion of atmospheric temperature and relative humidity vertical profiles in the East China region. An atmospheric temperature and humidity inversion model is constructed, and the parameters are optimized to obtain a network model configuration with high inversion accuracy, resulting in all-weather, high-precision atmospheric temperature and relative humidity profile. According to the results, the following conclusions can be drawn. 1) Temperature inversion results of the model have a mean error (ME) between -1.00 K and 1.00 K at each pressure layer, except that the absolute value of ME in the lower layer of the cloudy sky is greater than 1.00 K. The validation experiment conducts on ERA5 data has root mean square error (RMSE) between 0 K and 2.00 K for most pressure layers, except for ~2.50 K at the 925?950 hPa layer, the minimum RMSE corresponds to the 200?500 hPa, indicating higher temperature inversion accuracy in the upper atmosphere. 2) For the inversion of atmospheric relative humidity, the ME of the lower and upper atmosphere is larger, whereas that of the middle atmosphere is smaller; RMSE is larger in the middle layers and smaller in the lower and upper layers. 3) Compared to clear sky condition, the accuracy of temperature and relative humidity inversion models under cloudy sky condition is slightly lower. 4) The deviation of the temperature and relative humidity inversion results from the sounding data is slightly greater than the deviation from the ERA5 data although the trend of error with height variation is similar. The HIRAS data generally performs well in inverting the temperature and relative humidity of clear and cloudy skies, with high inversion accuracy. Therefore, this study has important reference value for inversion methods and techniques of atmospheric temperature and relative humidity, providing useful insights for future related research.
Laser & Optoelectronics Progress
- Publication Date: Apr. 10, 2025
- Vol. 62, Issue 7, 0701001 (2025)
Sand-Dust Flux and Its Effect on Atmospheric Environment Based on Lidar Network
Minjuan Mao, Houtong Liu, Yilei Dong, Honglei Zhang, and Fangping Deng
The quantitative calculation of pollutant transport remains challenging in air-pollution research. Based on Mie's theory, a quantitative calculation method for calculating dust flux was established using lidar-network and surface-composition observations. Subsequently, it was applied to the quantitative analysis of sand-dust flux and the investigation of the effects on the atmospheric condition during the dust process from April 10 to 14, 2023. The results show that the total net inputs of PM10 and PM2.5 in Zhejiang province are 27894 t and 5930 t during the dust process, respectively, thus indicating that the input sand-dust primarily comprised coarse particulate matter. The net input of PM10 per unit area in Hangzhou-Jiaxing-Huzhou is the largest, i.e., 0.523 to 0.598 t·km-2, followed by those of Jinhua, Quzhou, and Lishui, i.e., 0.240, 0.235, and 0.114 t·km-2, respectively. Except Quzhou with 0.083 t·km-2 and Lishui with 0.049 t·km-2, the net inputs of PM2.5 per unit area in other areas are similar, ranging from 0.050 to 0.066 t·km-2. The input of sand dust increases the atmospheric particle concentration, decreases the PM2.5/PM10 ratio, and increases the depolarization ratio. However, these effects weakened gradually owing to the sedimentation of sand dust and the binding of urban aerosols during transport. Additionally, the contents of ozone, CO2, and CH4 decreased. The volume fractions of CO2 and CH4 no longer exhibit the daily variation characteristics of high during the day and low at night, which is attributable to the effect of sand-dust on meteorological conditions such as temperature and water vapor density. In summary, sand-dust input can provide soil supplementation, affect meteorological conditions, and mitigate the greenhouse effect. The quantitative calculation of pollutant transport remains challenging in air-pollution research. Based on Mie's theory, a quantitative calculation method for calculating dust flux was established using lidar-network and surface-composition observations. Subsequently, it was applied to the quantitative analysis of sand-dust flux and the investigation of the effects on the atmospheric condition during the dust process from April 10 to 14, 2023. The results show that the total net inputs of PM10 and PM2.5 in Zhejiang province are 27894 t and 5930 t during the dust process, respectively, thus indicating that the input sand-dust primarily comprised coarse particulate matter. The net input of PM10 per unit area in Hangzhou-Jiaxing-Huzhou is the largest, i.e., 0.523 to 0.598 t·km-2, followed by those of Jinhua, Quzhou, and Lishui, i.e., 0.240, 0.235, and 0.114 t·km-2, respectively. Except Quzhou with 0.083 t·km-2 and Lishui with 0.049 t·km-2, the net inputs of PM2.5 per unit area in other areas are similar, ranging from 0.050 to 0.066 t·km-2. The input of sand dust increases the atmospheric particle concentration, decreases the PM2.5/PM10 ratio, and increases the depolarization ratio. However, these effects weakened gradually owing to the sedimentation of sand dust and the binding of urban aerosols during transport. Additionally, the contents of ozone, CO2, and CH4 decreased. The volume fractions of CO2 and CH4 no longer exhibit the daily variation characteristics of high during the day and low at night, which is attributable to the effect of sand-dust on meteorological conditions such as temperature and water vapor density. In summary, sand-dust input can provide soil supplementation, affect meteorological conditions, and mitigate the greenhouse effect.
Laser & Optoelectronics Progress
- Publication Date: Mar. 10, 2025
- Vol. 62, Issue 5, 0501004 (2025)
Effect of Ocean Turbulence on Coherent Detection System for Partially Coherent Gaussian Schell Beams
Kai Hu, Zhiyuan Zhao, Pengcheng Zhao, Zhenkun Tan... and Pengfei Hou|Show fewer author(s)
Heterodyne detection is an efficient approach for weak signal detection in underwater optical communication. Based on the generalized Huygens-Fresnel diffraction principle, a coherent detection mathematical model for the propagation of partially coherent Gaussian Schell beams in ocean turbulence is established. The model considers the transmission characteristics of partially coherent Gaussian Schell beams, and an analytical expression for the heterodyne efficiency of partially coherent Gaussian Schell beams in ocean turbulence environments is derived. The effects of the light source parameters, ocean turbulence parameters, transmission distance, and detector aperture on the heterodyne efficiency are numerically investigated. The research results show that the effects of the light source parameters on the heterodyne efficiency are negligible when compared with that of the ocean turbulence. Moreover, increasing the detector aperture does not improve the heterodyne efficiency, although selecting an appropriate detector aperture can effectively suppress the ocean turbulence effect in an environment with a specific ocean turbulence intensity. Hence, the conclusions of this study provide theoretical guidance for coherent detection systems in underwater wireless optical communication. Heterodyne detection is an efficient approach for weak signal detection in underwater optical communication. Based on the generalized Huygens-Fresnel diffraction principle, a coherent detection mathematical model for the propagation of partially coherent Gaussian Schell beams in ocean turbulence is established. The model considers the transmission characteristics of partially coherent Gaussian Schell beams, and an analytical expression for the heterodyne efficiency of partially coherent Gaussian Schell beams in ocean turbulence environments is derived. The effects of the light source parameters, ocean turbulence parameters, transmission distance, and detector aperture on the heterodyne efficiency are numerically investigated. The research results show that the effects of the light source parameters on the heterodyne efficiency are negligible when compared with that of the ocean turbulence. Moreover, increasing the detector aperture does not improve the heterodyne efficiency, although selecting an appropriate detector aperture can effectively suppress the ocean turbulence effect in an environment with a specific ocean turbulence intensity. Hence, the conclusions of this study provide theoretical guidance for coherent detection systems in underwater wireless optical communication.
Laser & Optoelectronics Progress
- Publication Date: Mar. 10, 2025
- Vol. 62, Issue 5, 0501003 (2025)
Aerosol Optical Properties Measurement Using Terrestrial Ecosystem Carbon Inventory Satellite: Retrieval and Validation
Binglong Chen, Chenxing Zha, Yuegen Bian, Yijie Ren, and Lingbing Bu
Aerosols can alter the radiation balance of the Earth's atmosphere or affect the formation of clouds as condensation nuclei, thereby affecting the global atmosphere. Aerosol optical parameters can be used to investigate this effect. Spaceborne LiDAR systems are commonly used to obtain global aerosol optical parameters. In August 2022, China successfully launched the terrestrial ecosystem carbon inventory satellite (TECIS). The main payload of the satellite is a spaceborne multibeam LiDAR, which can observe aerosol optical parameters on a global scale. This system currently requires the comparative validation of observation results. Based on the Fernald forward-integration method, we retrieve the aerosol backscatter coefficient and depolarization ratio. Data from the micro pulse LiDAR network (MPLNET), cloud aerosol LiDAR, and infrared pathfinder satellite observation (CALIPSO) are used to compare the retrieval results of the algorithm. The results show that the aerosol optical parameters retrieved by the multibeam LiDAR are highly consistent with the data and that the R2 obtained from correlation analysis is approximately 0.8. This study preliminarily verifies the observation ability of the spaceborne multibeam LiDAR system for atmospheric aerosols in the TECIS. Aerosols can alter the radiation balance of the Earth's atmosphere or affect the formation of clouds as condensation nuclei, thereby affecting the global atmosphere. Aerosol optical parameters can be used to investigate this effect. Spaceborne LiDAR systems are commonly used to obtain global aerosol optical parameters. In August 2022, China successfully launched the terrestrial ecosystem carbon inventory satellite (TECIS). The main payload of the satellite is a spaceborne multibeam LiDAR, which can observe aerosol optical parameters on a global scale. This system currently requires the comparative validation of observation results. Based on the Fernald forward-integration method, we retrieve the aerosol backscatter coefficient and depolarization ratio. Data from the micro pulse LiDAR network (MPLNET), cloud aerosol LiDAR, and infrared pathfinder satellite observation (CALIPSO) are used to compare the retrieval results of the algorithm. The results show that the aerosol optical parameters retrieved by the multibeam LiDAR are highly consistent with the data and that the R2 obtained from correlation analysis is approximately 0.8. This study preliminarily verifies the observation ability of the spaceborne multibeam LiDAR system for atmospheric aerosols in the TECIS.
Laser & Optoelectronics Progress
- Publication Date: Mar. 10, 2025
- Vol. 62, Issue 5, 0501002 (2025)
Underwater Laser Spot Center Positioning Method Under Background Light Interference
Fengtao He, Shaohui Guo, Ruina Wang, Runan Liu... and Jianlei Zhang|Show fewer author(s)
To address the problem of inaccurate identification of the receiving end caused by background light interference on the transmitting light source in underwater wireless optical communication, an underwater laser spot circle fitting center positioning algorithm is proposed based on a random sampling consensus algorithm. First, the spot image is preprocessed to obtain edge pixels. Then, a random sampling consensus algorithm is used to eliminate the interference of noisy data points, and finally, a circle fitting algorithm is used to position the spot center with high precision. Experimental verification was conducted by shooting laser spot images in water in the presence of background light interference. The results show that compared with the traditional centroid method and circle fitting algorithm, the improved algorithm significantly reduces the impact of background light on the positioning of the light source center. In the x direction, the positioning error was approximately 2 pixel, and the minimum error was only 0.49 pixel; in the y direction, the error was approximately 1 pixel, and the minimum error was only 0.04 pixel. The average coordinate deviation was 1.805 pixel, and the root mean square error for the calculated spot center coordinates was 2.2063 pixel, demonstrating the low deviation, high accuracy, and good anti-interference ability of the improved algorithm. To address the problem of inaccurate identification of the receiving end caused by background light interference on the transmitting light source in underwater wireless optical communication, an underwater laser spot circle fitting center positioning algorithm is proposed based on a random sampling consensus algorithm. First, the spot image is preprocessed to obtain edge pixels. Then, a random sampling consensus algorithm is used to eliminate the interference of noisy data points, and finally, a circle fitting algorithm is used to position the spot center with high precision. Experimental verification was conducted by shooting laser spot images in water in the presence of background light interference. The results show that compared with the traditional centroid method and circle fitting algorithm, the improved algorithm significantly reduces the impact of background light on the positioning of the light source center. In the x direction, the positioning error was approximately 2 pixel, and the minimum error was only 0.49 pixel; in the y direction, the error was approximately 1 pixel, and the minimum error was only 0.04 pixel. The average coordinate deviation was 1.805 pixel, and the root mean square error for the calculated spot center coordinates was 2.2063 pixel, demonstrating the low deviation, high accuracy, and good anti-interference ability of the improved algorithm.
Laser & Optoelectronics Progress
- Publication Date: Mar. 10, 2025
- Vol. 62, Issue 5, 0501001 (2025)
Research on Underwater Transmission and Communication of Airy Beam
Changxun Liu, Jiamin Sun, Xiangnian Shang, Yongjian Gu, and Wendong Li
To address problems of a high loss of optical beam energy, weak optical beam quality, and weak communication performance in underwater wireless optical communication, an experimental system is setup to carry out comparative experiments of the transmission for Airy beam and ordinary Gaussian beam in water channel, as well as comparative experiments of the single-photon detection communication in an 80-meter water channel. Experimental results show that the abilities of the Airy beam to maintain beam quality and to resist beam dithering in water channel are evidently superior to those of the Gaussian beam. Compared to the Gaussian beam, the adoption of the Airy beam in communication can increase the effective frame ratio by ~11.15% and reduce the error rate by ~42.52%. Results prove the superior performance of the Airy beam to the Gaussian beam in underwater optical communication, thus providing a possibility for long distance and high performance underwater optical communication. To address problems of a high loss of optical beam energy, weak optical beam quality, and weak communication performance in underwater wireless optical communication, an experimental system is setup to carry out comparative experiments of the transmission for Airy beam and ordinary Gaussian beam in water channel, as well as comparative experiments of the single-photon detection communication in an 80-meter water channel. Experimental results show that the abilities of the Airy beam to maintain beam quality and to resist beam dithering in water channel are evidently superior to those of the Gaussian beam. Compared to the Gaussian beam, the adoption of the Airy beam in communication can increase the effective frame ratio by ~11.15% and reduce the error rate by ~42.52%. Results prove the superior performance of the Airy beam to the Gaussian beam in underwater optical communication, thus providing a possibility for long distance and high performance underwater optical communication.
Laser & Optoelectronics Progress
- Publication Date: Feb. 10, 2025
- Vol. 62, Issue 3, 0301002 (2025)
Discussion on Calibration Constants of Water Vapor Inversion Process of Raman Lidar
Wenhui Wang, and Nianwen Cao
Water vapor plays an important role in the earth-atmosphere system, and the change of water vapor is an important reference for the change of weather and climate. Raman lidar has outstanding performance and is widely used in water vapor detection. It is very important to determine the calibration constant term in the inversion of water vapor mixing ratio detected by Raman lidar. It is common to use the radiosonde data to determine the calibration constant. However, the cost of simultaneous release of sounding balloons is high, and the radiosonde data of the global radiosonde network is limited in time and space. Compared with radiosonde data, ERA5 reanalysis data has higher spatiotemporal resolution and wider coverage. Many scholars analyze and apply ERA5 reanalysis data, which verifies that ERA5 reanalysis data is in good agreement with radiosonde data. Therefore, this paper proposes to use ERA5 reanalysis data to determine the calibration constant at the place and time without radiosonde data. The calibration constant of water vapor inversion with Raman lidar is determined by ERA5 water vapor data in Hefei. In the altitude range of 0.5?2 km, the calibration constant changes with time and altitude, which is considered to be caused by data deviation, interpolation calculation and lidar system error. The relative error between the inversion results and ERA5 data is mostly within ±10% by substituting the mean profile of the adjacent time calibration constants. Water vapor plays an important role in the earth-atmosphere system, and the change of water vapor is an important reference for the change of weather and climate. Raman lidar has outstanding performance and is widely used in water vapor detection. It is very important to determine the calibration constant term in the inversion of water vapor mixing ratio detected by Raman lidar. It is common to use the radiosonde data to determine the calibration constant. However, the cost of simultaneous release of sounding balloons is high, and the radiosonde data of the global radiosonde network is limited in time and space. Compared with radiosonde data, ERA5 reanalysis data has higher spatiotemporal resolution and wider coverage. Many scholars analyze and apply ERA5 reanalysis data, which verifies that ERA5 reanalysis data is in good agreement with radiosonde data. Therefore, this paper proposes to use ERA5 reanalysis data to determine the calibration constant at the place and time without radiosonde data. The calibration constant of water vapor inversion with Raman lidar is determined by ERA5 water vapor data in Hefei. In the altitude range of 0.5?2 km, the calibration constant changes with time and altitude, which is considered to be caused by data deviation, interpolation calculation and lidar system error. The relative error between the inversion results and ERA5 data is mostly within ±10% by substituting the mean profile of the adjacent time calibration constants.
Laser & Optoelectronics Progress
- Publication Date: Feb. 10, 2025
- Vol. 62, Issue 3, 0301001 (2025)
Impulse Response of ICESat-2 Satellite LiDAR System and Inversion Study of Ocean Optical Parameters
Zheng Zhao, Zhiyu Zhang, and Songhua Wu
The ICESat-2 satellite carries the world's first photon-counting system LiDAR system, i.e., the advanced topographic laser altimeter system (ATLAS), whose high repetition frequency and multibeam design can provide water-profile data with high spatial resolutions. However, the water-profile signals acquired by the ATLAS exhibits "after pulse" which restricts the application of the observation data and must be corrected using an inverse convolution algorithm, where an appropriate system impulse-response function is the core of the inverse convolution algorithm. In this study, the possible sources of "after pulse" are first identified, based on which the requirements of the system impulse-response function in the deconvolution are clarified through theoretical derivation, and a data-quality control algorithm is proposed on this basis, and the system impulse-response function is established using salt-marsh and desert data. Based on an analysis of ex-Gaussian fitting results, the pulse widths of the system impulse-response functions established using the desert and salt-marsh data are 0.095 and 0.142, a difference of 0.047, which can be reduced to 0.002 using quality-control methods. Subsequently, the system impulse-response functions generated from the two types of surface data are used to back-convolute the water body signals and invert the backward scattering coefficients of the water body and particulate matter. Finally, the inversion results show that in the Black Sea waters, without quality control, the inversion error of the system impulse-response function based on salt-marsh data is smaller, whereas after quality control, the inversion results using desert and salt-marsh data as the system impulse response-function indicate similar errors. The ICESat-2 satellite carries the world's first photon-counting system LiDAR system, i.e., the advanced topographic laser altimeter system (ATLAS), whose high repetition frequency and multibeam design can provide water-profile data with high spatial resolutions. However, the water-profile signals acquired by the ATLAS exhibits "after pulse" which restricts the application of the observation data and must be corrected using an inverse convolution algorithm, where an appropriate system impulse-response function is the core of the inverse convolution algorithm. In this study, the possible sources of "after pulse" are first identified, based on which the requirements of the system impulse-response function in the deconvolution are clarified through theoretical derivation, and a data-quality control algorithm is proposed on this basis, and the system impulse-response function is established using salt-marsh and desert data. Based on an analysis of ex-Gaussian fitting results, the pulse widths of the system impulse-response functions established using the desert and salt-marsh data are 0.095 and 0.142, a difference of 0.047, which can be reduced to 0.002 using quality-control methods. Subsequently, the system impulse-response functions generated from the two types of surface data are used to back-convolute the water body signals and invert the backward scattering coefficients of the water body and particulate matter. Finally, the inversion results show that in the Black Sea waters, without quality control, the inversion error of the system impulse-response function based on salt-marsh data is smaller, whereas after quality control, the inversion results using desert and salt-marsh data as the system impulse response-function indicate similar errors.
Laser & Optoelectronics Progress
- Publication Date: Jan. 10, 2025
- Vol. 62, Issue 1, 0101001 (2025)
Ocean-Land Waveform Classification Based on Multichannel Weighted Voting of Airborne Green Laser
Xinglei Zhao, Gang Liang, Jianhu Zhao, and Fengnian Zhou
In order to improve the accuracy of ocean-land waveform classifications of airborne green lasers in complex ocean-land environments, an ocean-land waveform classification method based on multichannel weighted voting [i.e., multichannel weighted voting convolutional neural network (MWV-CNN)] is proposed. First, the multichannel green laser waveforms collected in the deep and shallow channels are input into the proposed one-dimensional convolutional neural network (1D CNN) module through a multichannel input module. Second, each 1D CNN module processes each channel waveform separately to obtain the predicted scores for each channel waveform belonging to the ocean and land categories. Finally, the predicted score of each channel is treated as weight, and a multichannel fusion module is used to determine the final waveform category via weighted voting. The measured data in the coastal waters of Lianyungang, China are verified by experiment using Optech CZMIL. The results indicate that the overall classification accuracy, Kappa coefficient, and overall accuracy standard deviation of MWV-CNN are 99.45%, 0.982, and 0.02%, respectively, and as compared with traditional ocean-land waveform classification methods, the proposed method exhibits better classification accuracy and robustness, thus providing a new effective way for realizing ocean-land waveform classification of airborne green laser with high accuracy. In order to improve the accuracy of ocean-land waveform classifications of airborne green lasers in complex ocean-land environments, an ocean-land waveform classification method based on multichannel weighted voting [i.e., multichannel weighted voting convolutional neural network (MWV-CNN)] is proposed. First, the multichannel green laser waveforms collected in the deep and shallow channels are input into the proposed one-dimensional convolutional neural network (1D CNN) module through a multichannel input module. Second, each 1D CNN module processes each channel waveform separately to obtain the predicted scores for each channel waveform belonging to the ocean and land categories. Finally, the predicted score of each channel is treated as weight, and a multichannel fusion module is used to determine the final waveform category via weighted voting. The measured data in the coastal waters of Lianyungang, China are verified by experiment using Optech CZMIL. The results indicate that the overall classification accuracy, Kappa coefficient, and overall accuracy standard deviation of MWV-CNN are 99.45%, 0.982, and 0.02%, respectively, and as compared with traditional ocean-land waveform classification methods, the proposed method exhibits better classification accuracy and robustness, thus providing a new effective way for realizing ocean-land waveform classification of airborne green laser with high accuracy.
Laser & Optoelectronics Progress
- Publication Date: May. 10, 2024
- Vol. 61, Issue 9, 0901004 (2024)
Optical Coupling Performance in Free Space Based on Grating-Type Optical Waveguide
Pengfei Wu, Hanying Liu, and Sichen Lei
Spatial optical couplings in atmospheric turbulence channels are associated with low efficiencies and difficult alignments, hence, in this study, a research scheme for coupling a turbulent signal beam into optical waveguides through a grating was proposed and the influence of atmospheric turbulence on spatial light and optical waveguide coupling parameters was analyzed. Moreover, a highly efficient spatial optical coupling waveguide chip was designed by optimizing the structural parameters of the grating. Additionally, three sets of Si/SiO2 mirrors were introduced to reduce the downward coupling loss and further improve the grating coupling efficiency. Simulation results show that for the spatial light affected by atmospheric turbulence, the coupling efficiency of the incident grating coupler at 1550 nm was 74% (50.5%, without adding the mirrors) when the grating period, etching depth, and lower cladding thickness were 660 nm, 100 nm, and 1.45 μm, respectively, indicating the efficient coupling of spatial light in the atmospheric turbulent channels. The findings of this study will be of great significance in improving the communication efficiency and photoelectric integration in the field of free-space optical communication. Spatial optical couplings in atmospheric turbulence channels are associated with low efficiencies and difficult alignments, hence, in this study, a research scheme for coupling a turbulent signal beam into optical waveguides through a grating was proposed and the influence of atmospheric turbulence on spatial light and optical waveguide coupling parameters was analyzed. Moreover, a highly efficient spatial optical coupling waveguide chip was designed by optimizing the structural parameters of the grating. Additionally, three sets of Si/SiO2 mirrors were introduced to reduce the downward coupling loss and further improve the grating coupling efficiency. Simulation results show that for the spatial light affected by atmospheric turbulence, the coupling efficiency of the incident grating coupler at 1550 nm was 74% (50.5%, without adding the mirrors) when the grating period, etching depth, and lower cladding thickness were 660 nm, 100 nm, and 1.45 μm, respectively, indicating the efficient coupling of spatial light in the atmospheric turbulent channels. The findings of this study will be of great significance in improving the communication efficiency and photoelectric integration in the field of free-space optical communication.
Laser & Optoelectronics Progress
- Publication Date: May. 10, 2024
- Vol. 61, Issue 9, 0901003 (2024)
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