To analyze the characteristics of drought and flood variations in Quanzhou during recent 55 years, the standardized precipitation index (SPI) and Empirical Orthogonal Function (EOF) and Rotated Empirical Orthogonal Fu...To analyze the characteristics of drought and flood variations in Quanzhou during recent 55 years, the standardized precipitation index (SPI) and Empirical Orthogonal Function (EOF) and Rotated Empirical Orthogonal Function (REOF) were calculated by using the monthly precipitation data from 6 meteorological bureaus across Quanzhou for 1960-2014. Results showed that: 1) During 1960-2014, the drought and flood showed Periodic variation characteristics in Quanzhou, the specific period of frequent drought was 1963-1972, 1977-1986 and 2009-2011, and the specific period of frequent flood was 1961-1962, 1972-1975, 1990-1992 and 1997-2007;the drought and flood did not have significant tendency of variation in Spring and Summer, and the drought and flood showed a non-significant downward trend in Autumn and Winter. 2) The drought and flood variation had relatively consistent trend in Quanzhou, but there was a big difference on the northwest mountainous area, the middle semi-mountainous area and the southeast coast area in some periods. 3) The precipitation cell and distribution in every season were Nan’an and Anxi, but there was a big difference in rainfall less area: it was Yongchun and Dehua in Spring, Chongwu and Jinjiang in Summer, Chongwu in Autumn, Dehua and Chongwu in Winter.展开更多
Light detection and ranging(LiDAR)serves as one of the key components in the fields of autonomous driving,surveying mapping,and environment detection.Conventionally,dense points clouds are pursued by LiDAR systems to ...Light detection and ranging(LiDAR)serves as one of the key components in the fields of autonomous driving,surveying mapping,and environment detection.Conventionally,dense points clouds are pursued by LiDAR systems to provide high-definition 3D images.However,the LiDAR is typically used to produce abundant yet redundant data for scanning the homogeneous background of scenes,resulting in power waste and excessive processing time.Hence,it is highly desirable for a LiDAR system to“gaze”at the target of interest by dense scanning and rough sparse scans on the uninteresting areas.Here,we propose a LiDAR structure based on an optical phased array(OPA)with reconfigurable apertures to achieve such a gaze scanning function.By virtue of the cascaded optical switch integrated on the OPA chip,a 64-,128-,192-,or 256-channel antenna can be selected discretionarily to construct an aperture with variable size.The corresponding divergence angles for the far-field beam are 0.32°,0.15°,0.10°,and 0.08°,respectively.The reconfigurable-aperture OPA enables the LiDAR system to perform rough scans via the large beam spots prior to fine scans of the target by using the tiny beam spots.In this way,the OPA-based LiDAR can perform the“gaze”function and achieve full-range scanning efficiently.The scanning time and power consumption can be reduced by 1/4 while precise details of the target are maintained.Finally,we embed the OPA into a frequency-modulated continuous-wave(FMCW)system to demonstrate the“gaze”function in beam scanning.Experiment results show that the number of precise scanning points can be reduced by 2/3 yet can obtain the reasonable outline of the target.The reconfigurable-aperture OPA(RA-OPA)can be a promising candidate for the applications of rapid recognition,like car navigation and robot vision.展开更多
Bessel beam featured with self-healing is essential to the optical sensing applications in the obstacle scattering environment.Integrated on-chip generation of the Bessel beam outperforms the conventional structure by...Bessel beam featured with self-healing is essential to the optical sensing applications in the obstacle scattering environment.Integrated on-chip generation of the Bessel beam outperforms the conventional structure by small size,robustness,and alignment-free scheme.However,the maximum propagation distance(Z_(max))provided by the existing approaches cannot support long-range sensing,and thus,it restricts its potential applications.In this work,we propose an integrated silicon photonic chip with unique structures featured with concentrically distributed grating arrays to generate the Bessel-Gaussian beam with a long propagation distance.The spot with the Bessel function profile is measured at 10.24m without optical lenses,and the photonic chip’s operation wavelength can be continuously performed from 1500 to 1630 nm.To demonstrate the functionality of the generated Bessel-Gaussian beam,we also experimentally measure the rotation speeds of a spinning object via the rotational Doppler Effect and the distance through the phase laser ranging principle.The maximum error of the rotation speed in this experiment is measured to be 0.05%,indicating the minimum error in the current reports.By the compact size,low cost,and mass production potential of the integrated process,our approach is promising to readily enable the Bessel-Gaussian beam in widespread optical communication and micro-manipulation applications.展开更多
Optical phased array(OPA)technology is considered a promising solution for solid-state beam steering to supersede the traditional mechanical beam steering.As a key component of the LIDAR system for long-range detectio...Optical phased array(OPA)technology is considered a promising solution for solid-state beam steering to supersede the traditional mechanical beam steering.As a key component of the LIDAR system for long-range detection,OPAs featuring a wide steering angle and high resolution without beam aliasing are highly desired.However,a wide steering range requires a waveguide pitch less than half of the wavelength,which is easily subjected to cross talk.Besides,high resolution requires a large aperture,and it is normally achieved by a high count number of waveguides,which complicates the control system.To solve the mentioned issues,we design two high-performance 128-channel OPAs fabricated on a multilayered SiN-on-SOI platform.Attributed to the nonuniform antenna pitch,only 128 waveguides are used to achieve a 4 mm wide aperture.Besides,by virtue of innovative dual-level silicon nitride(Si_(3)N_(4))waveguide grating antennas,the fishbone antenna OPA achieves a 100°×19.4°field of view(FOV)with divergence of 0.021°×0.029°,and the chain antenna OPA realizes a 140°×19.23°FOV with divergence of 0.021°×0.1°.To our best knowledge,140°is the widest lateral steering range in two-dimensional OPA,and 0.029°is the smallest longitudinal divergence.Finally,we embed the OPA into a frequency-modulated continuous-wave system to achieve 100 m distance measurement.The reflected signal from 100 m distance is well detected with 26 dBm input transmitter power,which proves that OPA serves as a promising candidate for transceiving optical signal in a LIDAR system.展开更多
文摘To analyze the characteristics of drought and flood variations in Quanzhou during recent 55 years, the standardized precipitation index (SPI) and Empirical Orthogonal Function (EOF) and Rotated Empirical Orthogonal Function (REOF) were calculated by using the monthly precipitation data from 6 meteorological bureaus across Quanzhou for 1960-2014. Results showed that: 1) During 1960-2014, the drought and flood showed Periodic variation characteristics in Quanzhou, the specific period of frequent drought was 1963-1972, 1977-1986 and 2009-2011, and the specific period of frequent flood was 1961-1962, 1972-1975, 1990-1992 and 1997-2007;the drought and flood did not have significant tendency of variation in Spring and Summer, and the drought and flood showed a non-significant downward trend in Autumn and Winter. 2) The drought and flood variation had relatively consistent trend in Quanzhou, but there was a big difference on the northwest mountainous area, the middle semi-mountainous area and the southeast coast area in some periods. 3) The precipitation cell and distribution in every season were Nan’an and Anxi, but there was a big difference in rainfall less area: it was Yongchun and Dehua in Spring, Chongwu and Jinjiang in Summer, Chongwu in Autumn, Dehua and Chongwu in Winter.
基金Program for Jilin University Science and Technology Innovative Research Team(2021TD-39)Jilin Provincial Development and Reform Commission Project(2020C056)+2 种基金Major Scientific and Technological Program of Jilin Province(20210301014GX)National Natural Science Foundation of China(62105173,62105174,61934003,62090054)National Key Research and Development Program of China(2022YFB2804504)。
文摘Light detection and ranging(LiDAR)serves as one of the key components in the fields of autonomous driving,surveying mapping,and environment detection.Conventionally,dense points clouds are pursued by LiDAR systems to provide high-definition 3D images.However,the LiDAR is typically used to produce abundant yet redundant data for scanning the homogeneous background of scenes,resulting in power waste and excessive processing time.Hence,it is highly desirable for a LiDAR system to“gaze”at the target of interest by dense scanning and rough sparse scans on the uninteresting areas.Here,we propose a LiDAR structure based on an optical phased array(OPA)with reconfigurable apertures to achieve such a gaze scanning function.By virtue of the cascaded optical switch integrated on the OPA chip,a 64-,128-,192-,or 256-channel antenna can be selected discretionarily to construct an aperture with variable size.The corresponding divergence angles for the far-field beam are 0.32°,0.15°,0.10°,and 0.08°,respectively.The reconfigurable-aperture OPA enables the LiDAR system to perform rough scans via the large beam spots prior to fine scans of the target by using the tiny beam spots.In this way,the OPA-based LiDAR can perform the“gaze”function and achieve full-range scanning efficiently.The scanning time and power consumption can be reduced by 1/4 while precise details of the target are maintained.Finally,we embed the OPA into a frequency-modulated continuous-wave(FMCW)system to demonstrate the“gaze”function in beam scanning.Experiment results show that the number of precise scanning points can be reduced by 2/3 yet can obtain the reasonable outline of the target.The reconfigurable-aperture OPA(RA-OPA)can be a promising candidate for the applications of rapid recognition,like car navigation and robot vision.
基金supported by National Key R&D Program of China under Grants no.2022YFB2804504The National Natural Science Foundation of China under Grants nos.62090054,61934003,62105173 and 62105174+1 种基金Major scientific and technological program of Jilin Province under Grants nos.20200501007GX and 20210301014GXProgram for JLU Science and Technology Innovative Research Team(JLUSTIRT,2021TD-39).
文摘Bessel beam featured with self-healing is essential to the optical sensing applications in the obstacle scattering environment.Integrated on-chip generation of the Bessel beam outperforms the conventional structure by small size,robustness,and alignment-free scheme.However,the maximum propagation distance(Z_(max))provided by the existing approaches cannot support long-range sensing,and thus,it restricts its potential applications.In this work,we propose an integrated silicon photonic chip with unique structures featured with concentrically distributed grating arrays to generate the Bessel-Gaussian beam with a long propagation distance.The spot with the Bessel function profile is measured at 10.24m without optical lenses,and the photonic chip’s operation wavelength can be continuously performed from 1500 to 1630 nm.To demonstrate the functionality of the generated Bessel-Gaussian beam,we also experimentally measure the rotation speeds of a spinning object via the rotational Doppler Effect and the distance through the phase laser ranging principle.The maximum error of the rotation speed in this experiment is measured to be 0.05%,indicating the minimum error in the current reports.By the compact size,low cost,and mass production potential of the integrated process,our approach is promising to readily enable the Bessel-Gaussian beam in widespread optical communication and micro-manipulation applications.
基金National Key Research and Development Program of China(2016YFE0200700)National Natural Science Foundation of China(61627820,61934003,62090054,62105173,62105174)+2 种基金Jilin Scientific and Technological Development Program(20200501007GX)Program for Jilin University Science and Technology Innovative Research Team(JLUSTIRT,2021TD-39)Guangdong Basic and Applied Basic Research Foundation(2019A1515111206)。
文摘Optical phased array(OPA)technology is considered a promising solution for solid-state beam steering to supersede the traditional mechanical beam steering.As a key component of the LIDAR system for long-range detection,OPAs featuring a wide steering angle and high resolution without beam aliasing are highly desired.However,a wide steering range requires a waveguide pitch less than half of the wavelength,which is easily subjected to cross talk.Besides,high resolution requires a large aperture,and it is normally achieved by a high count number of waveguides,which complicates the control system.To solve the mentioned issues,we design two high-performance 128-channel OPAs fabricated on a multilayered SiN-on-SOI platform.Attributed to the nonuniform antenna pitch,only 128 waveguides are used to achieve a 4 mm wide aperture.Besides,by virtue of innovative dual-level silicon nitride(Si_(3)N_(4))waveguide grating antennas,the fishbone antenna OPA achieves a 100°×19.4°field of view(FOV)with divergence of 0.021°×0.029°,and the chain antenna OPA realizes a 140°×19.23°FOV with divergence of 0.021°×0.1°.To our best knowledge,140°is the widest lateral steering range in two-dimensional OPA,and 0.029°is the smallest longitudinal divergence.Finally,we embed the OPA into a frequency-modulated continuous-wave system to achieve 100 m distance measurement.The reflected signal from 100 m distance is well detected with 26 dBm input transmitter power,which proves that OPA serves as a promising candidate for transceiving optical signal in a LIDAR system.
