Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
Adaptive demodulation of reflection spectrum intensity of fiber grating link
Qin Genchao, Meng Fanyong, Li Hong, Zhuang Wei, Dong Mingli
Accepted Manuscript  doi: 10.3788/IRLA20200440
[Abstract](294) [FullText HTML](174)
In view of the large difference in the intensity of single channel multi-grating reflection spectrum of demodulator, which leads to the failure of peak-seeking or the increase of peak-seeking error, a method of multiple exposure demodulation in different exposure cycles was proposed to adjust the peak value, and the peak-seeking threshold was determined according to the histogram of the spectral data. The influence of peak value of spectrum on the stability of peak-seeking was analyzed, the adaptive adjustment rules of exposure cycle and peak-seeking threshold were established, and the adaptive peak-seeking demodulation algorithm was realized by LabVIEW software. Through the actual fiber grating sensor test, the automatic exposure and peak-seeking demodulation of the reflection spectrum with too large difference could be completed. On the premise of ensuring the peak-seeking stability, the number of spectral peak identification, the adaptive ability of the demodulation system and the working reliability were effectively improved. The experimental results show that the peak stability is the highest when the peak value is in the range of 70%-90% of the saturation intensity. The standard deviation of the center wavelength obtained by peak-seeking is within 0.5 pm, the stability is increased by 50% compared with single exposure demodulation, and the program running time is within 100 ms, which can realize fast demodulation.
Research on ultra-low power consumption methane detection system based on NDIR technology
Zhao Qingchuan
Accepted Manuscript  doi: 10.3788/IRLA20200140
[Abstract](426) [FullText HTML](233)
In order to meet the needs of low power consumption methane detection technology, an ultra-low power consumption infrared methane sensor and system based on non-dispersed infrared spectroscopy is developed, which is based on the characteristics of methane gas molecules having main absorption peak in the infrared band of 3.2 μm~3.4 μm. The selection of LED and PD devices and the design of optical path are studied based on the analysis of the principle of infrared differential detection. The power consumption of infrared methane sensor is reduced to 10 mW by using LED packets of pulses current drive technology. The influence of temperature change on the measurement of methane concentration is studied by experimental method, the temperature compensation algorithm formula is obtained by data analysis and linear fitting of normalization method. The performance experiment is carried out on the detection system platform, and the basic performance parameters are given. The system has the advantages of low power consumption, anti-interference of water vapor and good detection stability, and has important application value.
Accepted Manuscript
[Abstract](3203) [FullText HTML](1195)
Depolarization Mechanism and Compensation Scheme of Radially Polarized Beams
YANG Ce, PENG Hong-pan, CHEN Meng, MA Ning, XUE Yao-yao, DU Xin-biao, ZHANG Xie
Accepted Manuscript  doi: 10.3788/IRLA202049.20200038
[Abstract](1190) [FullText HTML](2098)
Depolarization mechanism and compensation scheme of radially polarized beams under non-uniform pumping are investigated. Theoretical analysis shows that, for the non-uniform pumping status, the thermal induced shear birefringence caused by the thermally induced shear stress within the cross-section of the isotropic crystal is the main reason for the depolarization of the radially polarized beams. Related experiments were designed to evaluate the depolarization of the radially polarized beams which under non-uniform pumping conditions by using two methods of thin-film polarizer (TFP) measurement and purity measurement, in which the TFP measurement method is used to detect the overall depolarization of radially polarized beams and the purity measurement method is used to detect local depolarization of radially polarized beams. With a peak pump power of 1.1 kW, the depolarization measured by the two evaluation methods is 2.34% and 2.53%, respectively. Based on the theoretical analysis and evaluation results, a combination of phase modulation and spatial mode matching was considered in the design of the depolarization compensation scheme, which improved the depolarization of the radially polarized beams by 59%. Meanwhile, a picosecond radially polarized beam with a pulse energy of 19.36 mJ, a purity of 90.13%, and a beam quality M2 factor of 3.8 was achieved.
Numerical study on backward light amplification and damage in high-power fiber laser
Sheng Quan, Si Hanying, Zhang Haiwei, Zhang Junxiang, Ding Yu, Shi Wei, Yao Jianquan
Accepted Manuscript
[Abstract](4425) [FullText HTML](2349)
The amplification of both continuous-wave (CW) and pulsed backward signal in high-power master-oscillator-power-amplifier based fiber laser are investigated using rate equation model. The results show that the CW backward light would be amplified significantly by the high-power amplifier and thus decrease the laser output seriously. For the pulsed backward signal, the pulse energy would not be amplified obviously since the energy storage is absent in CW fiber laser. Considering the damage threshold of the fiber and devices including end-cap and fiber Bragg grating (FBG), the amplification of CW backward light may damage the FBG of the laser oscillator, and the backward laser pulse with millijoule level pulse energy may damage the fiber, while there also exists the risk of end-cap damage when pulsed backward laser incidents.
Thermal damage of monocrystalline silicon irradiated by long pulse laser
Guo Ming, Zhang Yongxiang, Zhang Wenying, Li Hong
Accepted Manuscript
[Abstract](306) [FullText HTML](222)
In view of the thermal damage law and mechanism of monocrystalline silicon for millisecond pulsed laser, the temperature of monocrystalline silicon irradiated by millisecond pulsed laser is measured by high precision point temperature meter and spectral inversion system. Then the temperature evolution process is analyzed. Also, the temperature state during the whole process of thermal damage of monocrystalline silicon irradiated by millisecond pulsed laser and the corresponding damage structure are studied. The results of this study show that the peak temperature of laser-induced monocrystalline silicon increases with the increase of energy density when the pulse width is fixed, When the pulse width is between 1.5 ms-3.0 ms, The temperature decreases with the increase of pulse width. Temperature rise curve shows inflection point when it is close to the melting point (1687 K), the reflection coefficient is from 0.33 to 0.72. During the gasification and solidification stages, it also shows the gasification and the solidification plateau periods. Thermal cleavage damage of monocrystalline silicon precedes thermal erosion damage. Stress damage dominates under low energy density laser irradiation, while thermal damage dominates under high energy density laser irradiation. The damage depth is proportional to the energy density and increases rapidly with the increase of the number of pulses.
Lasers & Laser optics
Infrared technology and application
Long-distance recognition of infrared quantum dot materials
Geng Rui, Zhao Kang, Chen Qingshan
2021, 50(7): 20200436.   doi: 10.3788/IRLA20200436
[Abstract](0) [FullText HTML](0) [PDF 1515KB](1)
Quantum dots are widely used in laser energy, photoelectric detection and other fields due to its unique photoelectric properties. Its size-dependent stimulated emission and flexible application form also make it an ideal fluorescent labeling material, which has attracted much attention in the fields of biomedicine, micromaterial detection, anti-counterfeiting and target recognition. In the field of anti-counterfeiting and target recognition where the application scenes are mostly macro natural environments, it is inevitable to detect and analyze the infrared fluorescence of quantum dots at a relatively long distance. Therefore, a long-distance detection system of infrared fluorescence for quantum dot was established based on weak signal detection technology and used to detect the fluorescence of PbS colloidal quantum dot films. The effective detection range of the fluorescence at 1300 nm for the samples was over 100-200 meters and may increase further. This meant that long-distance recognition of infrared quantum dot materials was realized. The detection results can be used to analyze and guide the preparation process of different infrared quantum dot materials, which will also promote the diversified development of their remote recognition applications.
Ship smoke detection method based on saliency and dense optical flow
Yang Zilong, Zhu Fuping, Tian Jinwen, Tian Tian
2021, 50(7): 20200496.   doi: 10.3788/IRLA20200496
[Abstract](0) [FullText HTML](0) [PDF 1137KB](0)
Ship targets are important objects for marine monitoring, and infrared imaging system has been widely used in ship inspection systems due to its feature of working at the same time during the day and night. However, infrared imaging systems will be easily affected by the release of smoke screens, which result in the invalidation of ship detection systems. Therefore, timely and effective detection of the smoke interference area in the infrared ship image is of great significance for accurate ship target detection. Aiming at the problem of detecting the interference of smoke area from ships in infrared images, a smoke detection method based on the fusion of saliency and dense optical flow was proposed in the paper. Because the smoke screen released by the ship was obviously different from the background, the AC algorithm of multi-scale neighborhood filtering was firstly used to detect the saliency area of the image, and the significant smoke screen area was extracted. Then, the movement characteristics of the smoke screen were used to compare the front and back frame of the image sequences, and the frame dense optical flow was calculated to obtain the motion information of the image. By setting the threshold to filter the obvious motion points, expand the motion point area, merge the split motion areas, the motion smoke area was obtained. Finally, the saliency area and the motion area were fused, and the final smoke screen area was obtained. The experimental results show that the method can effectively detect the smoke screen area, and is able to adapt to the changes of the reflected light of smoke screens and the background brightness variations.
Infrared dynamic scene generation of rocket plume observed by satellite
Liu Hao, Liu Dong, Mao HongXia, Xiao ZhiHe
2021, 50(7): 20200519.   doi: 10.3788/IRLA20200519
[Abstract](0) [FullText HTML](0) [PDF 2460KB](1)
A dynamic scene generation model for continuous observation of rocket in boost phase by infrared sensor in absorption band of satellite was established. A method of generating high-resolution surface emissivity images at band 22 and 23 of MODIS data based on neural networks was proposed. According to the proposed method, surface emissivity images with resolution of 100 meters were generated. Spectral emissivity of 4.18-4.5 μm was calculated by spectral correlation method; flight trajectories of rocket in boost phase were generated by Runge-Kutta method, and plume radiation transmission was calculated by LOS method to generate rocket plume image. The geometric relationship among rocket plume, surface points and the sensor on satellite was established. The plume and background were projected and imaged, and the dynamic scene of the rocket plume observed by the satellite was synthesized. By analyzing the radiance image sequences, it was found that radiances of the ground background was suppressed. At the same time, the target radiance contrast and the number of pixels occupied at different times were analyzed combined with the trajectory data. Furthermore, the difference of total radiation intensity curve of plume in different scenes was analyzed. The results show that the scene generation method is accurate and reliable, which can provide data basis and target characteristics support for target detection and tracking research based on images observed by satellite.
Optical design
Design of underwater large field of view zoom optical system
Qu Rui, Yang Jianfeng, Cao Jianzhong, Liu Bo
2021, 50(7): 20200468.   doi: 10.3788/IRLA20200468
[Abstract](0) [FullText HTML](0) [PDF 1478KB](0)
Under the requirements of an underwater large field of view zoom optical system, the selection of optical window and its influence on objective lens were discussed, by which the relative distortion and lateral color induced by the plane window were analyzed and corresponding design methods were given. Regarding the special envelope and working distance requirements of the underwater optical system, a three-part zoom system design model and the design method of the corresponding focusing components were provided by introducing aberration stabilizers in the PNNP structure, dynamic aberration correction capability of the optical structure was improved, also, the problems of the cam curve breakpoints were avoided; by setting the focus lens group in the objective parts, close-range imaging through the entire zoom range was guaranteed. A 4 K underwater large field of view zoom optical system was completed using 3840×2160 high-sensitivity CMOS detector, with 0.5 m-inf working distance, 0.48−0.64 μm work waveband, constant F number of up to 2.8 and 5.9°−62° full field of view. The image quality and tolerance characters are validated by an assembled lens and its underwater imaging experiments.
Detection method of mirror seeing based on curvature/ slope hybrid sensing
An Qichang, Wu Xiaoxia, Zhang Jingxu, Li Hongwen, Chen Lu
2021, 50(7): 20200419.   doi: 10.3788/IRLA20200419
[Abstract](0) [FullText HTML](0) [PDF 1552KB](0)
With the increase of aperture of optical elements, the influence of mirror seeing has become more and more difficult to ignore in the process of processing inspection and observation. For strong turbulence, slope detection is used to qualitatively analyze low order components. After the airflow is stable, curvature sensor can be used for fine measurement. After the slope detection, the back-end optical path of the autocollimator can be focused, and the system can be defocused to a certain amount (the defocusing direction of the two autocollimators is opposite), that is, the estimation of wavefront curvature can be obtained by the differential of wavefront along the optical axis. After obtaining the data, the results can be statistically analyzed based on point source sensitivity (PSSn) theory. Firstly, the basic method of curvature/slope hybrid sensing was deduced theoretically. The normalized PSSn was proposed by the US 30-meter telescope (TMT) to evaluate the overall performance, shape and distribution of systematic error and the change of mirror tranquility in the detection process were further analyzed with the PSSn as the evaluation index, the PSSn introduced by turbulence is 0.9718. The experimental results show that when the thermal disturbance flow field is relatively uniform, the influence of specular visibility on the flow field changes little with repeated changes. The work can quantitatively analyze the specular visibility of large-aperture optical elements, which is of great guiding significance for the optimization of large-aperture system design and detection processing.
Optical telescope of space debris detection and ranging compound system
Li Xiang, Bai Dongwei, Meng Lixin, Gao Liang, An Yan
2021, 50(7): 20200464.   doi: 10.3788/IRLA20200464
[Abstract](0) [FullText HTML](0) [PDF 1829KB](0)
In the ground verification demonstration experiment of the space debris detection and ranging composite system, the working environment is 10-30 ℃, the size limit of the optical base station (not exceeding 450 mm×400 mm) and the installation of the tail of the optical telescope cause the center of gravity to be far away from the mounting surface. Design of optical telescope for space debris detection and ranging compound system was proposed. The finite element model of the optical telescope was established by using ANSYS finite element analysis software. The analysis was carried out under the conditions of ambient temperature of 10-30 ℃, tail installation, optical axis direction and vertical optical axis direction of 1 g (g = 9.8 m/s2) gravity acceleration. The analysis results show that the first-order mode of the optical telescope is 133 Hz and the dynamic stiffness is better. When the gravity is in the direction of the optical axis, the maximum change in the distance between the primary and secondary mirrors is 0.01 mm. When the gravity is perpendicular to the optical axis, the maximum distance between the primary and secondary mirrors is 0.007 mm. The RMS value of the wave aberration of the optical telescope system is λ/15, and the maximum inclination angle of the secondary mirror is 1.93″. It has good power and thermal stability and can meet the index requirements in the process of optical antenna installation, calibration, testing and field experiment verification. After the optical telescope is assembled and calibrated, the image quality of the optical telescope is tested using a ZYGO interferometer. The test is performed under the conditions of gravity perpendicular to the optical axis and ambient temperature of 10 ℃, 20 ℃, and 30 ℃. The results show that the RMS value of the system wave phase difference is respectively at 0.097λ, 0.075λ and 0.1λ, the RMS value of the wave phase difference of the whole optical telescope system is better than λ/10 at the lowest temperature and the highest temperature, and all meet the requirements of the system.
Optimal design of silicon-based optical phased array sector antenna
Zhang Yaoyuan, Wang Rui, Jiang Ruitao, Du Kunyang, Li Yuanyang
2021, 50(7): 20210013.   doi: 10.3788/IRLA20210013
[Abstract](0) [FullText HTML](0) [PDF 1568KB](0)
In the optical phased array chip, the performance of the antenna unit directly determines the efficiency of the light wave energy in the waveguide to radiate outward. On this basis, the optimized design was mainly for the sector antenna. By adding a shallow etching area and a thin silicon strip to the sector antenna, the downward diffraction loss and back reflection loss of the antenna were suppressed, as well as the upward diffraction of the antenna was greatly improved. In addition, design schemes were formulated for the design requirements of improving the upward diffraction efficiency and reducing the design size. For the high diffraction efficiency scheme, the upward diffraction efficiency of the antenna reached 81.6%, the downward diffraction efficiency was reduced to 4%, and the back reflection was reduced to 1.4%. For the miniaturization scheme, the upward diffraction efficiency of the antenna was 67.2%, the downward diffraction was reduced to 5.6%, and the back reflection was reduced to 1.2%, which greatly improved the integration and emission efficiency of the optical phased array chip.
Optical imaging
Research on multispectral correlation imaging of moving target based on phase modulation
Li Meixuan, Wang Hong, Liu Xiaohan, Liu Ming, Song Lijun
2021, 50(7): 20210184.   doi: 10.3788/IRLA20210184
[Abstract](0) [FullText HTML](0) [PDF 1576KB](0)
In order to overcome the inability of scanning multi-spectral imaging to capture multi-spectral data in dynamic scenes, a single-exposure multispectral imaging method for moving targets was proposed based on phase modulation. This method combined associated imaging technology, compressed sensing technology and spectral imaging, introduced a spatial random phase modulator into the imaging light path, modulated and compressed the three-dimensional map information data of the moving target object, then used the two-dimensional aliasing signal obtained by the detector to reconstruct the three-dimensional map information to achieve a single exposure and simultaneously obtained the three-dimensional map information of the moving target. It had the advantages of high utilization rate of light energy, short imaging time, and simple system structure. The experimental results show that when the average electron number of a single frame of CCD detection signal increases from 200 e at intervals of 100 e to 1300 e, as the average rRMSE value of the electron number increases, the relative root mean square error of the reconstructed image decreases correspondingly, and the reconstruction improved image quality; when the stepper motor drives the target object to continuously move at a speed of 30 Hz, a multi-spectral reconstructed image of the moving object with better quality can be obtained; a spectrometer is used to test the spectral distribution curves of different spectrum bands in the target object, and the results obtained are basically consistent with the spectral distribution curves of the reconstructed image, which proves the effectiveness of the method. The research results provide a useful reference for the application of multi-spectral correlation imaging technology in UAV platforms, dynamic monitoring and other fields.
Optical communication and sensing
Signal feature extraction method based on MEEMD-HHT for distributed optical fiber vibration sensing system
Yu Miao, Zhang Yaolu, Xu Zechen, He Yutong
2021, 50(7): 20210223.   doi: 10.3788/IRLA20210223
[Abstract](0) [FullText HTML](0) [PDF 17207KB](0)
In practical application, the signals measured by distributed optical fiber vibration sensing system are mostly non-stationary random signals, and the key to realize pattern recognition is to obtain the amplitude-time-frequency instantaneous characteristics of the signals accurately. Existing related research shows that Hilbert transform combined with empirical mode decomposition can obtain the instantaneous energy and instantaneous frequency of the intrinsic modal component of measuring signal. The subsequent improved ensemble empirical mode decompostion method, has pseudo component and large reconstruction error, while complementary ensemble empirical mode decompostion method reduces the reconstruction error, but increases the amount of computation, which cannot guarantee the efficiency and accuracy of feature extraction and classification. In this paper, the feature extraction of distributed optical fiber vibration sensing system was realized based on modified ensemble empirical mode decompostion with Hilbert transform, the evaluation mechanism of permutation entropy was introduced to optimize the iteration times of random noise in the decomposition process. Through simulation analysis and experimental comparison, it was verified that the method could effectively solve the problems existing in the above methods and improve the system's performance in processing time and feature accuracy. Experimental results show that the average extraction accuracy of the proposed method for single-frequency vibration signals is 99.2%. Compared with EMD and CEEMD, the average feature extraction accuracy of mixed vibration signal is 98.1%, which is 15.6% and 7% higher than EMD and CEEMD respectively. The average time of the algorithm is the shortest, which is 3.8259 s. It provides a reliable and efficient method for signal feature extraction of distributed fiber vibration sensing system.
Research on end force measurement method of soft robot based on fiber Bragg grating
Tang Chen, He Yanlin, Zhu Lianqing, Sun Guangkai
2021, 50(7): 20200386.   doi: 10.3788/IRLA20200386
[Abstract](0) [FullText HTML](0) [PDF 1574KB](1)
The measurement of the terminal operating force of the surgical robot is the key to achieve the precise control of the robot, which is crucial to ensure the safety of the surgical operation. In this paper, a method of measuring the three-dimensional force of soft robot terminal end based on fiber Bragg grating was proposed to meet the requirement of minimally invasive surgery. Based on the principle of fiber grating sensing, the sensing characteristics of fiber sensor embedded in soft robot were analyzed and a soft robot terminal force decoupling model based on linear calibration with least square method and nonlinear compensation with Bernstein polynomial was established. Then the relationship between the central wavelength shift of the fiber Bragg grating and the three-dimensional force at the end of the soft robot was studied. The results show that the average repeatability of FBG sensor is 1.5 pm. The measurement accuracy error of the end force in the three directions of XYZ is lower than 5% of the full range, and the residual distribution is mostly concentrated in the reliable range, with good repeatability. The proposed FBG decoupling algorithm provides an effective method for the precise measurement of the terminal force of soft robot in minimally invasive surgery, and has a promising application prospect in the measurement of the terminal force of soft robot in biomedicine.
Design of optical system of high isolation laser communication terminal
Wang Xiaoyan, Xu Gaokui
2021, 50(7): 20200521.   doi: 10.3788/IRLA20200521
[Abstract](0) [FullText HTML](0) [PDF 1323KB](0)
Laser communication has outstanding advantages such as large information capacity, high optical gain, high anti-interference and anti-interception capabilities. It was an important technical means to solve high-speed communication problems. According to the requirements of transceiver isolation and two-way duplex working mode in laser communication. After simulating and analyzing the isolation of different optical structures, it was proposed to use off-axis three-mirror optical antennas to reduce backscattering to achieve high transceiver isolation. In the optical design, the smallest incident angle on the optical surface was controlled through iterative optimization, and clear index requirements were put forward for the fine processing technology of the optical surface, and finally the isolation was more than 70 dB. The simulation analysis shows that the object field angle of 5 mrad isolation is 73.7 dB, and the measured isolation of Φ150 mm off-axis three-mirror optical antenna can reach 73 dB, which is consistent with the results of simulation analysis. It meets the requirements of satellite laser communication system tracking and communication for light antenna isolation, and can be used for inter-satellite laser communication.
Special issue on microwave photonics $ Commentary
Prospects of cross research between microwave photonics and multidiscipline (Invited)
Li Ming, Hao Tengfei, Li Wei
2021, 50(7): 20211042.   doi: 10.3788/IRLA20211042
[Abstract](1) [FullText HTML](0) [PDF 1012KB](1)
Microwave photonics can be used for the generation, processing, receiving and distribution of microwave signals based on optoelectronic devices, with advantages such as broad bandwidth, low loss, light weight, fast reconfigurability and immunity to electromagnetic interference. With the rapid development of the theory and technology of microwave photonics, cross research between microwave photonics and multidiscipline has been the key of its direction of development. The research status of cross research between microwave photonics and some disciplines was summarized, and prospects of cross research between microwave photonics and disciplines such as laser technology, integrated optoelectronics, quantum technology and artificial intelligence were provided.
Optoelectronic harmonized integration technology for intelligent processing of signal and information (Invited)
Zou Weiwen, Ma Bowen, Xu Shaofu, Zou Xiuting
2021, 50(7): 20211043.   doi: 10.3788/IRLA20211043
[Abstract](2) [FullText HTML](0) [PDF 921KB](0)
Traditional signal and information processing technologies are relatively independent and complicated. Artificial intelligence (AI) technology introduces a processing scheme of signal conversion plus information recognition to improve the level of intelligence in system processing. However, a high intensity of signals and information in future applications demand for more efficient systems and more flexible decision-making capabilities. It was proposed that optoelectronic integration technology was promising to realize the processing of signal and information as a new processing paradigm. Taking the complementary advantages of photonic and electronic technologies in electromagnetic scales, physical advantages, and practical implementations, overall and direct processing of signal and information was achieved and had the potential to integrate deeper levels of intelligence technology. Emerging signal and information processing paradigms enabled by optoelectronic integration were reviewed. The supportive significance of optoelectronic hybrid integration on optoelectronic integration processing technology was demonstrated.
Photonic microwave measurements (Invited)
Lu Bing, Zou Xihua
2021, 50(7): 20211044.   doi: 10.3788/IRLA20211044
[Abstract](0) [FullText HTML](0) [PDF 871KB](1)
Microwave signal detection and analysis are the key technologies for electrical information systems like communication, radar, electronic warfare. With the rapid development of new information technology, microwave photonic technology combines the advantages of both lightwave and microwave, which is characterized by the advantages of large bandwidth, low loss and anti-electromagnetic interference. In this paper, a comprehensive overview of the microwave photonic measurements, especially photonic-assisted microwave frequency measurement schemes based on frequency-amplitude mapping, frequency-to-time mapping, and Optical channelization was introduced. In addition, the corresponding problems and prospects were briefly summarized.
Special issue on microwave photonics $ Letters
Wideband large dispersion group delay chip based on silicon photonics integration (Invited)
Chen Hongwei, Du Zhenmin, Fu Tingzhao, Yang Sigang, Chen Minghua
2021, 50(7): 20211045.   doi: 10.3788/IRLA20211045
[Abstract](0) [FullText HTML](0) [PDF 1133KB](0)
Content integrated, broadband, large group delay devices have important applications in microwave photonic filtering, true delay phased array antenna and other fields, which can effectively reduce the system size and power consumption. In this paper, a broadband large dispersion delay chip based on silicon-based photonic integration was proposed and implemented. By using ultra-low loss waveguide structure and side wall normal vector modulation structure, on-chip integration of large dispersion waveguide grating was realized. The dispersion was about 250 ps/nm, maximum group delay was 2440 ps and the bandwidth was more than 9.4 nm. The chip is expected to be used in microwave photonics, high-speed fiber communication system and other fields.
Novel microwave photonic applications based on integrated microcombs (Invited)
Xue Xiaoxiao, Zheng Xiaoping
2021, 50(7): 20211046.   doi: 10.3788/IRLA20211046
[Abstract](0) [FullText HTML](1) [PDF 1137KB](0)
Microresonator-based frequency combs (microcombs) are very promising for microwave photonic applications for their advantages including wide bandwidth, large line spacing, and compact volume. Recently, various microcomb-based microwave photonic systems have been reported such as high-spectral-purity microwave generation, microwave photonic signal processing, true-time-delay beamforming, etc. Outstanding performances including low phase noise, high reconfigurability, and large Nyquist bandwidth have been demonstrated, showing a bright future of microcomb-based microwave photonics.
High-performance thin-film electro-optical modulator based on heterogeneous silicon and lithium niobate platform (Invited)
Sun Shihao, Cai Xinlun
2021, 50(7): 20211047.   doi: 10.3788/IRLA20211047
[Abstract](0) [FullText HTML](0) [PDF 877KB](0)
Silicon photonic integration platform has attracted extensive attention in the field of optical communication due to its high integration and CMOS process compatibility. As one of the most important devices in optical communication system, electro-optic modulator plays a key role in loading electrical signals onto optical signals. To break the performance limitation of silicon-based modulator, the large-area bonding technology of silicon and lithium niobate and the low loss waveguide etching technology of lithium niobate can be used to achieve high-performance thin film electro-optic modulator based on heterogeneous silicon and lithium niobate platform. At present, this kind of modulator with the best performance exhibits a half-wave voltage of 3 V, a 3 dB electro-optical bandwidth of more than 70 GHz, an insertion loss of less than 1.8 dB, and an extinction ratio of more than 40 dB. In this paper, the research status of integrated modulator based on silicon and lithium niobate heterogeneous platform was compared and the structure design and fabrication process of the heterogeneous integrated thin-film modulator were introduced respectively.
Special issue on microwave photonics $ Review articles
Frontiers and prospects of integrated microwave photonics (Invited)
Li Ming, Hao Tengfei, Pan Shilong, Zou Xihua, Yun Binfeng, Zou Weiwen, Li Wei, Yan Lianshan
2021, 50(7): 20211048.   doi: 10.3788/IRLA20211048
[Abstract](0) [FullText HTML](0) [PDF 2114KB](0)
Microwave photonics is an interdisciplinary subject of microwave engineering and photonics technology. It is a fused microwave and optical system that studies the interaction between optical and microwave signals in the medium and the generation, processing, transmission, and receiving of microwave signals in the optical domain. Integration is an inevitable trend of microwave photonics since the performances of current discrete devices-based microwave photonic systems are poor in terms of size, power consumption, stability and cost. The main scientific and technical issues of integrated microwave photonics were discussed, its development status and frontier research progresses were summarized, and an outlook of its future prospects was given.
Application and development of microwave photonics in electronic warfare (Invited)
Zhou Tao, Li Tao, Xie Aiping, He Ziang, Xu Jiaxin, Li Rui
2021, 50(7): 20211049.   doi: 10.3788/IRLA20211049
[Abstract](0) [FullText HTML](0) [PDF 1414KB](1)
The electronic warfare is a key force of the information war, whose capabilities can be enhanced based on microwave photonics (MWP) technology due to the broadband, high speed, parallelism, and compactness. Microwave photonics technology, as applied to electronic warfare systems, involves the signal generation, transmission, and processing. Firstly, the mission and capability requirements of electronic warfare were presented, and the core elements affecting the effectiveness of electronic warfare was analyzed. Secondly, the advantages of MWP applied to the electronic warfare were discussed in detail. Taking the optical beam forming as an example, MWP technology overcomes the beam-squinting effect. Finally, towards the transition from electronic warfare to electromagnetic spectrum warfare, the challenges and development trend of MWP were proposed.
Exploration and preliminary application of high throughput satellite with microwave photonics (Invited)
Li Li, Tan Qinggui
2021, 50(7): 20211050.   doi: 10.3788/IRLA20211050
[Abstract](0) [FullText HTML](1) [PDF 1171KB](1)
The High Throughput Satellite (HTS) is the major developing and application direction of the new generation wideband communication satellite. The domestic and neighborhood market have a huge demand of HTS. The characteristics and development demands with microwave photonics of HTS were analyzed. The main research developments, especially the new developments of HTS in our country, were introduced. The applications of microwave photonics on HTS and the foreign microwave photonics payloads of HTS were studied. And a new microwave photonics payload scheme was proposed and studied. The effectiveness and feasibility of this microwave photonics payload scheme were tested. In the end, the problems and suggestion of microwave photonics HTS were analyzed.
Special issue on microwave photonics $ Research articles
Broadband array radar based on microwave photonic frequency multiplication and de-chirp receiving (Invited)
Zhang Fangzheng, Gao Bindong, Pan Shilong
2021, 50(7): 20211051.   doi: 10.3788/IRLA20211051
[Abstract](1) [FullText HTML](0) [PDF 1741KB](1)
Microwave photonic radar enables the generation and processing of broadband radar signals, which can significantly improve the range resolution of the radar system. To improve the radar angle resolution and realize flexible beam control, combining microwave photonic radar technology with array radar technology is an inevitable development trend. Previously, the optical truth delay technology is intensively investigated to achieve squint-free beam steering in broadband phased array radars, which usually face the problems of high complexity, poor flexibility, and limited delay accuracy. In recent years, the broadband radar architecture based on microwave photonic frequency multiplication and de-chirp receiving has received extensive attention. The array radar constructed based on this technology has wide operation bandwidth while enabling real-time digital compensation and processing functions, which provides a new idea for the development of broadband array radars. In this paper, the research progress of the broadband array radar based on microwave photonic frequency multiplication and de-chirp processing was reviewed. After expounding the transceiver mechanism of microwave photonic broadband radar, the method for constructing broadband phased array radar and the performance of digital beam scanning and imaging were introduced. Then, the radar array was extended to MIMO architecture. The broadband microwave photonic MIMO radar based on optical wavelength division multiplexing technology was introduced and its performance in target detection and imaging was analyzed.
Research on ultra-wideband and high saturation power uni-traveling carrier photodetectors (Invited)
Xiong Bing, Chao Enfei, Luo Yi, Sun Changzheng, Han Yanjun, Wang Jian, Hao Zhibiao, Wang Lai, Li Hongtao
2021, 50(7): 20211052.   doi: 10.3788/IRLA20211052
[Abstract](0) [FullText HTML](0) [PDF 1531KB](1)
Ultra-wideband uni-traveling carrier (UTC) photodetectors have broadband advantages over traditional PIN detectors, as only fast electrons are required to transport in UTC photodetectors. They will be one of the key optoelectronic devices in the sub-terahertz systems, such as 6G broadband wireless communications, terahertz imaging, ultra-wideband noise generators, etc. For the requirements of optoelectronic conversion in sub-terahertz frequency band, high-speed photo-generated carrier transport mechanics and inductive coplanar waveguide (CPW) structure were studied to improve the device bandwidth and saturation power of the photodetector. A dual-drift layer structure MUTC photodetector chip with bandwidth of 106 GHz, saturated output power of 7.3 dBm, and a CPW-optimized MUTC photodetector chip with bandwidth over 150 GHz were developed.
Harmonically mode-locked optoelectronic oscillator (Invited)
Zeng Zhen, Zhang Zhiyao, Zhang Lingjie, Zhang Shangjian, Li Heping, Liu Yong
2021, 50(7): 20211053.   doi: 10.3788/IRLA20211053
[Abstract](1) [FullText HTML](0) [PDF 1681KB](1)
An actively mode-locked optoelectronic oscillator (OEO) scheme was proposed to generate high-repetition-rate microwave pulse signals based on high-order harmonic mode locking. In the proposed scheme, the bias port of the electro-optic intensity modulator in the cavity was driven by a sinusoidal signal. The frequency of the sinusoidal signal (${f_{bias}}$) was set to be $N$ times of the free spectral range of the OEO cavity to realize fundamental ($N = 1$) and harmonic ($N \geqslant 2$) mode locking, where the repetition rate of the generated microwave pulse signal was equal to ${f_{bias}}$. In the proof-of-concept experiment, 10th-, 50th- and 100th-order harmonic mode locking were realized, where the repetition rate of the generated microwave pulse signal was 360 kHz, 1.8 MHz and 3.6 MHz, respectively. The proposed actively mode-locked OEO scheme provides a new way to generate low-phase-noise microwave pulse signals for pulse Doppler radar application.
Research on channelized synthesis of ultra-wideband radio frequency signal based on dual optical frequency combs (Invited)
Yin Feifei, Yin Zikai, Xie Xiangzhi, Dai Yitang, Xu Kun
2021, 50(7): 20211054.   doi: 10.3788/IRLA20211054
[Abstract](0) [FullText HTML](0) [PDF 1236KB](0)
With the development of the modern communication system, broadband and high-frequency microwave radio frequency (RF) signals have been widely applied in the fields of radar, communication and signal processing. Based on the microwave photonic channelization, ultra-wideband RF signals were generated through dual optical frequency combs (OFCs) with different free spectrum ranges (FSRs). In the channelized synthesis system, multiple independent narrowband signal was input in each channel for up-conversion and detected by multi-heterodyne detection to reconstruct a wideband RF signal with continuous spectrum. In multi-heterodyne detection, interference suppression technique increased the highest frequency that the synthesized RF signal could reach. In the experiment, a wideband RF signal was synthesized with an instantaneous bandwidth of 4 GHz, covering a frequency range of 8.4-12.4 GHz. The experiment demonstrates an interference suppression ratio of 21 dB, indicating that the interference suppression technique increases the highest frequency of the output signal and effectively improves the spectrum utilization.
Research on full band real time Fourier transformation for 6G (Invited)
Li Jilong, Duan Xiangyang, Fan Chen, Lv Kailin, Zong Baiqing
2021, 50(7): 20211055.   doi: 10.3788/IRLA20211055
[Abstract](0) [FullText HTML](0) [PDF 1211KB](0)
In this paper, a scheme was proposed to achieve microwave photonic real time Fourier transformation based on spectrally-discrete dispersion, which aimed for the time-frequency information analysis of microwave signals in the future 6G wireless communication. The discrete dispersion media showed periodic narrowband filtering in the intensity frequency response and discrete quadratic phase distribution in the phase frequency response. Real time frequency to time mapping of microwave signals was then obtained using the discrete dispersion media. Furthermore, the time and frequency information of a non-stationary signal could be analyzed. Since only discrete phase shifts rather than continuously-changed true time delay were required, huge equivalent dispersion could be achieved with compact device to reduce the delay. An implementation based on cascaded ring resonators was proposed in this paper to achieve discrete dispersion, where fiber loops of 4 cm were used. Highly linear FTM with a slope of 0.8 ps/MHz was obtained through numerical stimulation, which was equivalent to 5800 km standard single-mode fiber. The resolution of the FTM reached 50 MHz and the unambiguous bandwidth reached 5 GHz. Taking the linear frequency modulation (LFM) signal which was often used in the convergence of sensing and communication in 6G as an example, the short-time Fourier transform function of the system was simulated to analyze the time and frequency information of the signal. The time resolution reached 20 ns, and the speed of spectrum analysis was as high as $ 2.5\times {10}^{8} $ FTs/s, which was significantly better than the traditional DSP based schemes.
Chip-based microwave photonic frequency mixer (Invited)
Li Simin, Cong Rong, Yao Xiaoxiao, Feng Jing, Tang Zhenzhou, Pan Shilong
2021, 50(7): 20211056.   doi: 10.3788/IRLA20211056
[Abstract](0) [FullText HTML](0) [PDF 1504KB](0)
A microwave photonic frequency mixer constituted of an optically-carried local oscillator (LO) and a wavelength-division modulator was proposed. The wavelength-division modulator chip, which was consisted of a silicon phase modulator, two micro-ring filters, a photodetector, two optical couplers, and two grating couplers, was designed and fabricated. Based on the chip, a microwave photonic harmonic frequency mixer was implemented. In the experiment, an optically-carried LO was generated by double-sideband suppressed-carrier modulation at a Mach-Zehnder modulator. An RF signal from 6 to 16 GHz was successfully converted into a signal with a frequency of 33 to 23 GHz. In order to suppress the remaining mixing spurs, two solutions, i.e., increasing the rejection ratio of the micro-ring filter to decrease the intensity of the leaked optically-carried LO and introducing an optical phase shifter to correct the phase of the leaked optically-carried LO, were proposed and verified by simulation. It should be noted that the latter is simpler and more suitable for photonic integration.
Nonlinear modification of dispersion delay for optical beam forming
Shao Guanghao, Liu Ang, Zhai Jiquan, Zhang Guoqiang
2021, 50(7): 20210235.   doi: 10.3788/IRLA20210235
[Abstract](0) [FullText HTML](0) [PDF 1166KB](0)
Optical beam forming network is an important part in optically controlled phased array radar, which could improve the beam scanning ability with large bandwidth and direction angle. The direction of beam is usually controlled by optical switches to change relative delay of transmitting and receiving channels. Among commonly-used techniques, dispersion delay is a concision way to realize optical beam forming network. Linear dispersion is only applicable to beam forming with limited dispersion delay and channels. With the increase of delay, nonlinear dispersion delay accumulates, which distorts the beamform. Therefore, relative dispersion slope (RDS) was used as a nonlinear factor. Moreover, adjusting wavelengths of commercial lasers was raised to compensate the nonlinearity. If RDS was 0.003 nm−1, the maximum wavelength interval stretched from 0.796 nm to 0.862 nm and wavelengths shifted −0.31 nm. In this case, maximum difference between modified and commercial laser wavelengths was 0.2 nm, which was suitable for the passband of commercial wavelength division multiplexing devices. In the meantime, ratio of main to side lobe improved from 5 dB to 12.9 dB with large scanning direction. Based on the analysis, the smaller RDS value was, the less wavelengths modifications of lasers were. Therefore, RDS is a key parameter in choosing dispersion material and adjusting wavelengths of lasers. In this way, distorted beamform could be recovered. The abilities of imaging and identifying thus could be improved in phase arrayed systems.
Lasers & Laser optics
2021, 50(7): 20210347.   doi: 10.3788/IRLA20210347
[Abstract](0) [FullText HTML](0) [PDF 689KB](0)
L-band switchable dual-wavelength, high-energy pulsed fiber laser
Wang Lisha, Sun Songsong, Yan Wei, Qu Jiaojiao, Wang Yong
2021, 50(7): 20200370.   doi: 10.3788/IRLA20200370
[Abstract](0) [FullText HTML](0) [PDF 1259KB](0)
An L-band switchable dual-wavelength, frequency stabilized, high energy, single frequency, single mode linearly polarized, pulsed laser based on a master osocillator power amplifier (MOPA) configuration was reported. It could be used as the emission source of detecting atmospheric CO2 LIDAR system. This pulsed fiber laser system was mainly composed of two single frequency narrow linewidth external cavity semiconductor lasers, pulse modulation system, and multi-stage fiber amplifiers. The wavelengths of 1572.018 nm and 1572.480 nm could be switched freely by controlling a magneto-optical switch. Using the closed loop temperature control technology, the locked central frequency and output optical power were implemented. The on-off extinction ratio of 80 dB was achieved by using digital and analog acousto-optic modulators in series. The Stimulated Brillouin Scattering (SBS) threshold was increased by applying non-uniform stress to the fiber. With a common commercial gain fiber and commercial polarization maintaining components, an average output power of 1.5 W, pulse width of 309 ns, the peak power of 485 W, pulse energy of 150 μJ and signal to noise ratio of 25 dB were generated at a repetition rate of 10 kHz and the wavelength of 1572 nm. The power consumption of the whole laser system which used air cooling was less than 60 W.
High-resolution three-dimensional imaging based on all-fiber photon-counting Lidar system
Guo Jingjing, Fei Xiaoyan, Ge Peng, Zhou Anran, Wang Lei, Li Zhengqi, Sheng Lei
2021, 50(7): 20210162.   doi: 10.3788/IRLA20210162
[Abstract](1) [FullText HTML](0) [PDF 2027KB](0)
A 1064 nm photon-counting Lidar system was experimentally demonstrated to realize high-resolution three-dimensional(3D) imaging all day. Herein, the optical system was composed of all-fiber components, which improved the system stability. Objects in long distance could be detected by Lidar system through whole machine scanning and the scanning view reached 360° in horizon and ±30° in azimuth direction. Also, the geometry distortion was avoided compared to swing mirror scanning. Additionally, the spatial resolution was increased by using a sub-pixel scanning method. Finally, 3D images could be reconstructed by a multi-range reconstruction algorithm with self-adaptive noise threshold. Results showed that a 3D object 3.1 km away was successfully reconstructed in daytime with clear features. The ranging accuracy was 0.11 m. The spatial resolution was about 0.11 m, beyond the diffraction limit of the optical system.
Application of Gaussian process model in SAR image target recognition
Shang Shanshan, Yu Zikai, Fan Tao, Jin Limin
2021, 50(7): 20200337.   doi: 10.3788/IRLA20200337
[Abstract](0) [FullText HTML](0) [PDF 1264KB](0)
The Gaussian process model was applied to synthetic aperture radar (SAR) image target recognition. Gaussian process model was a statistical learning algorithm based on the Bayesian framework, which combines the kernel function and probability judgement to build the classification model. Compared with the traditional classification models, the Gaussian process model could achieve higher classification accuracy and precision. In the implementation of target recognition, the feature vectors from SAR images were used as the inputs while the target labels were employed as the outputs thus training the Gaussian process model. For the test sample to be classified, the posterior probabilities related to different classes were calculated thus determining its target label. In the experiments, typical situations were set up to test the proposed method using the MSTAR dataset. According to the experimental results, the proposed method could achieve 99.28% recognition accuracy for 10 types of targets under standard operating conditions. The average recognition rates at 30° and 45° depression angles were 98.04% and 73.13%, respectively. Under noise corruption, the best performance was achieved by the proposed method at each noise level. The results validated the effectiveness and robustness of the proposed method.
Research on the development of detection satellite technology in the novel multi-beam land and ocean lidar
Wang Zijun, Zhang Yang, Liu Dong, Wang Xiaobo, Yuan Jinru, Pan Chao, Zhao Yiming, Han Xiaoshuang, Zhou Yudi, Liu Qun, Wang Cheng
2021, 50(7): 20211041.   doi: 10.3788/IRLA20211041
[Abstract](0) [FullText HTML](0) [PDF 1546KB](0)
Started with needs of the national strategy, the necessity of China’s oceanographic lidar developing was analyzed, the characteristics of the oceanographic lidar and domestic and overseas’ development of the spaceborne lidar’s were summarized, the future spaceborne ocean lidar’s development direction was put forward and expected on-orbit data application products was proposed. The key technology and solution of the spaceborne ocean lidar were discussed, the application prospect of developing the marine lidar was given during the 14th five year plan.
Laser preheating/fluid cooling assisted laser metal deposition of AlSi10Mg
Wan Le, Shi Shihong, Xia Zhixin, Zhang Xiaozu, Fu Geyan, Zhang Rongwei, Li Kuan
2021, 50(7): 20200365.   doi: 10.3788/IRLA20200365
[Abstract](0) [FullText HTML](0) [PDF 2377KB](0)
It is difficult to form aluminum alloy stablely by laser metal deposition(LMD) due to high thermal conductivity, low laser absorptivity, and significant heat accumulation effect. To realize automatic and accurate preheating, eliminating heat accumulation, analyzing the effect of preheating and improving the forming ability of AlSi10Mg aluminum alloy LMD, the technology of laser metal deposition with "internal powder feeding" and Ar supply protection was adopted, the laser preheating and fluid cooling temperature control system was designed and the preheating and cooling temperature control model was established, LMD forming experiments of AlSi10Mg aluminum alloy was carried out, the effects of preheating on laser absorptivity, surface quality, cross-section morphology, temperature field, microstructure and properties of aluminum alloy were systematically analyzed. The results show that the laser preheating and fluid cooling temperature control system can realize accurate preheating and eliminate heat accumulation, obtain a single track with a surface roughness Ra of 2.6 μm. High precision, high efficiency and stable LMD forming of AlSi10Mg overlap, block and thin-wall are realized. Preheating can improve the laser absorptivity, flatten the track and increase the grain size. The assist system and method can effectively solve the problem of insufficient forming stability of aluminum alloy LMD, and provide a new idea and process for forming quality control and molten temperature controlling.
Target detection technique of laser and millimeter wave dual-mode fused proximity detection
He Qigong, Jia Xiaodong
2021, 50(7): 20200361.   doi: 10.3788/IRLA20200361
[Abstract](0) [FullText HTML](0) [PDF 1547KB](0)
Aiming at the problems of complex background and strong environment adaptability of fuze system, a short-range detection method based on laser and millimeter wave fusion for the application background of sea target orientation recognition and anti-jamming of new generation anti-ship missile was proposed in this paper. Firstly, the shortcomings of single-mode detection system were introduced from the applicaion status of laser and millimeter wave in fuze. In view of this deficiency, a compound detection scheme based on the dual-mode fusion was proposed, and the detection system structure, accurate time identification algorithm of pulsed laser in dynamic scene and fusion target detection method were studied. In this method, the consistency and stability of laser detection performance in complex scenes could be achieved. And by introducing the distance information obtained from laser detection system into millimeter wave target detection algorithm simultaneously, the efficiency and reliability of the algorithm were effectively improved. Through theoretical simulation analysis, the results show that the method in this paper can make up for the shortcomings of single detection system in anti-jamming, and effectively improve the efficiency and reliability of target detection, which can provide reference for the subsequent anti-jamming system design of proximity fuze.
Situation and key technology of tactical laser anti-UAV
Zhu Mengzhen, Chen Xia, Liu Xu, Tan Chaoyong, Li Wei
2021, 50(7): 20200230.   doi: 10.3788/IRLA20200230
[Abstract](0) [FullText HTML](0) [PDF 2776KB](0)
The accident occurrence of UAV is increasing relatively with the development of it, which become a fatal threat to national defence and social security. Handling such problem has become a difficult mission for all countries. Conventional arms, due to the restriction, are hard to defend UAV. With the development of technology, tactical laser weapon is revealing great advantage in defending such aerocraft. In this article, the development and actuality of tactical laser anti-UAV are sorted out. The key technology in three aspects, which are high energy laser source includes high energy laser and beam combining, quisition tracking pointing, high efficient destroying, are analyzed and summarized. This article points out the developing direction of tactical laser anti-UAV, which could be considered as a reference as well.
Design of low-order Hartmann-Shack wavefront sensor for annular laser beam
Feng Yafei, Wei Chengfu, Liu Xiankui, Ren Xiaoming, Wang Zhenhua, Meng Zhaorong
2021, 50(7): 20210016.   doi: 10.3788/IRLA20210016
[Abstract](0) [FullText HTML](0) [PDF 1072KB](0)
Based on the fact that there were a large percentage of low-order aberrations which had large PV values in high-energy laser beam, a Hartmann-Shack wavefront sensor for measuring first five-order Zernike aberrations was presented and designed. The lens part of the sensor adopted a method with combination of a 6-units micro-lens array and a convex lens, and the micro-lens array was distributed in annular. Since the lens material of this sensor was GaF2, the designed sensor could be applied to the low-order aberrations measurement of visible and infrared laser beam. This method had the advantages of low cost, simple structure and large detection range, which was suitable for the measurement of large PV-value low-order aberrations of the annular laser beam. Afterwards, a measurement system for the low-order Hartmann-Shack wavefront sensor had been set up, and the results show that the measuring range was ±8λ (λ=3.39 μm) and the accuracy was less than λ/10 (λ=3.39 μm).