• Volume 42,Issue 6,2023 Table of Contents
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    • >Infrared Materials and Devices
    • High operating temperature p-on-n HgCdTe MWIR 1024×768 FPA detector

      2023, 42(6):711-715. DOI: 10.11972/j.issn.1001-9014.2023.06.001

      Abstract (279) HTML (61) PDF 1.12 M (1059) Comment (0) Favorites

      Abstract:Increasing the operating temperature for infrared detectors is critical to reduce the size, weight and power of infrared (IR) systems. Such systems are essential to implement a compact and low-cost production of IR systems. For the Kunming Institute of Physics (KIP), HgCdTe standard p-on-n technology with indium doping and arsenic ion implantation technology has been optimized for many years and mid-wavelength IR (MWIR) detectors with excellent electro-optical performance were realized. This paper reports the latest results of the MWIR focal plane array (FPA) detector with a high operating temperature (HOT). Performances of the 1024×768@10 μm pitch MW detector working above 150 K were presented. The detector presenting a cut-off wavelength above 4.97 μm at 150 K has been developed. The noise-equivalent temperature difference (NETD), dark current and operability at different operating temperatures were attained. Additionally, the IR image taken with the MWIR HgCdTe-based FPA and processed at an operating temperature of 150 K was presented and retained an operability of 99.4%.

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    • Study on photocurrent transport and quantum efficiency of interband cascade infrared photodetectors

      2023, 42(6):716-723. DOI: 10.11972/j.issn.1001-9014.2023.06.002

      Abstract (196) HTML (70) PDF 1.63 M (888) Comment (0) Favorites

      Abstract:The interband cascade infrared photodetector (ICIP) can achieve high operating temperature by using the multistage cascade absorption region. But different design of absorption region will cause the mismatch of photogenerated carriers, which will affect the quantum efficiency of the device. In order to better understand the influence of the stage and thickness of ICIP on quantum efficiency, we measure the performance of ICIP based on the type-II InAs/GaSb superlattice at different operating temperatures. And based on the “average effect” of photocurrent, a quantum efficiency model operating at reverse bias voltage is established. Compared with the measured results, it is found that the experimental data and the calculated results are in good agreement at low temperatures. It is verified that the photocurrent is the average of current at all stages based on the electrical gain. However, the experimental photocurrent at high temperatures is lower than the calculation. This may be due to the short minority carrier lifetime at high temperatures, and the photogenerated carrier recombination mechanism exists at the interface of the absorption region and the relaxation region.

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    • Studies of resonator-enhanced mid-infrared interband cascade light emitting diode

      2023, 42(6):724-729. DOI: 10.11972/j.issn.1001-9014.2023.06.003

      Abstract (151) HTML (94) PDF 1.16 M (776) Comment (0) Favorites

      Abstract:The mid-infrared light emitting diodes based on the interband cascade structure and resonant cavity structure are simulated and designed. Based on the traditional interband cascade LED, a distributed Bragg reflector (DBR) structure is introduced outside the device to form a resonant interband cascade LED. The parameters of the resonant cavity are simulated and optimized, including the number of DBR cycles, the length of the resonator, the position of the active region in the resonator, and the optimized device structure is obtained. The simulation results show that the device using ZnS/Ge DBR with one period as the upper mirror of the resonator has the highest output power. When the active region is located at the peak of the electric field intensity in the resonant cavity, the device will have the highest output power. The output power of the three-stage resonant cavity interband cascade LED device is equivalent to that of the 55-stage device without a resonant cavity. Meanwhile, the output light has a better direction, and the full width at half peak of the far field distribution can be reduced from 92 degrees to 52 degrees. Combined with the test results of the fabricated 5-stage interband cascade LED device, the simulation results after adding a resonant cavity structure indicate that the radiance of the peak wavelength is increased by 11.7 times, the integrated radiance is increased by 5.43 times, and the full-width at half-maximum is narrowed by 6.45 times.

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    • Bi composition-dependent study of infrared photoluminescence efficiency in InPBi bandgap

      2023, 42(6):730-735. DOI: 10.11972/j.issn.1001-9014.2023.06.004

      Abstract (183) HTML (49) PDF 1.32 M (691) Comment (0) Favorites

      Abstract:The photoluminescence (PL) transitions of the dilute-bismide InPBi originate mainly from the defect-related processes, and manifest the properties of long wavelength, broad linewidth and strong emission. To further clarify the PL efficiency issues, we carry out excitation power-dependent PL spectral analyses on a series of InPBi samples with different Bi compositions in this work. The PL lineshape changes significantly and the dominant emission redshifts as the Bi composition increases. Meanwhile, the excitation power-dependent evolution of the PL integral intensity indicates that the PL efficiency enhances firstly and then drops as the Bi composition rises, and reaches the maximum with a Bi composition of 0.5%. The enhancement of the PL efficiency is ascribed to the Bi trapping holes to lower the nonradioactive recombination on one hand, and to the Bi surfactant effect on the other hand. Nevertheless, the high Bi component brings excessive impurities and the Bi-related advantages are suppressed, which results in low PL efficiency. These results are beneficial to the understanding of the infrared emission performance of InPBi and suggest InPBi as a potential semiconductor for infrared optoelectronic applications.

    • Effects of embedded low-dimensional materials on resonant mode of distributed Bragg reflector cavity

      2023, 42(6):736-741. DOI: 10.11972/j.issn.1001-9014.2023.06.005

      Abstract (180) HTML (48) PDF 1.42 M (761) Comment (0) Favorites

      Abstract:Low-dimensional material embedded cavities have been widely used in nano-lasers and detectors etc. The effects of embedded materials on the cavity resonant mode need to be intensively studied for achieving the efficient coupling between the gain material and the cavity. The influences of embedded material thickness and position, cavity layer thickness and the number of distributed Bragg reflector pairs on the cavity resonant mode are discussed in this work. Results show that the cavity resonant mode changes periodically with different embedded positions and there is a maximum peak shift within a period of λ/2 optical path. The maximum peak shift decreases with increasing cavity thickness and is proportional to the embedded material thickness. The number of distributed Bragg reflector pairs does not affect the cavity resonant mode. These results provide guidance on the optical device design and the analysis of experimental phenomena, which can be applied to different wavelength ranges of distributed Bragg reflector cavity structures.

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    • Surface potential alignment in MoS2 and MoTe2 homo- and hetero-junctions

      2023, 42(6):742-746. DOI: 10.11972/j.issn.1001-9014.2023.06.006

      Abstract (209) HTML (68) PDF 1.04 M (817) Comment (0) Favorites

      Abstract:In transition metal dichalcogenides (TMD) flakes, the geometry, such as layer thickness, significantly tune the electronic properties, including bandgap, electron affinity and Fermi level. Such characteristic offers a high degree of freedom to tune the functionality of semiconductor device, once the volatile electronic properties are precisely determined. However, to date, there are still significant uncertainties in determining the Fermi-level alignment of TMD homo- or hetero- junctions, which might lead to significant deviations of band-bending and thus device performance. Here, we utilize the Scanning Kelvin Probe Microscopy (SKPM) to characterize the surface-potential/Fermi-level alignment of TMD homo- or hetero- junctions. Through this effort, a distinct phenomenon is verified where the Fermi-levels of MoS2 and MoTe2 shift towards the intrinsic level with an increasing layer thickness (in other words, the background doping concentration is continuously lowering). Moreover, we show the significant impact of surface contamination (molecular scale) on the surface potential of monolayer TMD. Finally, we fabricate a MoTe2/MoS2 heterojunction, in which we observe the wide depletion region and large photoresponse. Together, those findings might offer a reference to precisely stack van der Waals (vdW) layers as designed for both electronic and optoelectronic applications.

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    • >Terahertz and Millimeter Wave Technology
    • Research on watt-level power combining technology at terahertz band based on bonding wire compensation

      2023, 42(6):747-754. DOI: 10.11972/j.issn.1001-9014.2023.06.007

      Abstract (208) HTML (55) PDF 2.98 M (913) Comment (0) Favorites

      Abstract:With the application demands of solid-state high power in the terahertz (THz) band, a THz-band watt-level power output is achieved by adopting GaN power amplifier (PA) MMIC and power combining technology. Microstrip-waveguide transition, and the low-loss interconnection based on the gold wire compensation are used to package a PA module composed of two PA MMICs and an E-plane T-junction two-way power splitter/combiner. Maximum output power of 160 mW is achieved. Based on the module and an eight-way E-plane combiner, a sixteen-way power combining amplifier is designed across the frequency range of 180 to 238 GHz. Output power of more than 300 mW is achieved with +10 V drain voltage, and the maximum power is 1.03 W at 189 GHz.

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    • Faraday rotation in nitrogen-doped diamond measured by polarized terahertz time-domain spectroscopy in the presence of strong magnetic field

      2023, 42(6):755-761. DOI: 10.11972/j.issn.1001-9014.2023.06.008

      Abstract (192) HTML (47) PDF 1013.74 K (901) Comment (0) Favorites

      Abstract:Nitrogen (N)-doped diamond (N-D) is one of the most important carbon-based electronic materials and has many interesting and unique features in terms of physics owing to the presence of N related color centers. In this paper, the terahertz (THz) magneto-optical (MO) properties of N-D grown by microwave plasma chemical vapor deposition (MPCVD) are investigated. By using polarized THz time-domain spectroscopy (TDS) in the presence of magnetic field from 0 to 8 T, the THz transmission through an N-D sample in Faraday geometry is measured at 80 K. The dependence of the Faraday rotation angle and ellipticity, the complex transverse or Hall MO conductivity and the complex dielectric constant upon the magnetic field for N-D are examined. The results show that N-D has excellent THz MO Faraday rotation effect and can be applied as THz rotatory material.

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    • Progress in the study of nonlinear dynamic characteristics based on quantum cascade lasers

      2023, 42(6):762-770. DOI: 10.11972/j.issn.1001-9014.2023.06.009

      Abstract (171) HTML (47) PDF 1.16 M (820) Comment (0) Favorites

      Abstract:Quantum Cascade Laser (QCL) is a unipolar semiconductor laser that relies on the excitation of photons radiated by electrons leaping between subbands of quantum wells. Numerous theoretical and experimental studies have demonstrated that slight external perturbations (optical feedback, optical injection) or sufficiently strong internal nonlinear mode couplings can induce nonlinear output of semiconductor lasers. QCL, as a new type of semiconductor device, is characterized by high intracavity strength, strong inter-subband optical nonlinearity and fast electron relaxation time, which has stimulated the interest in studying its nonlinear dynamics. In this paper, we review in detail the progress of the study of nonlinear dynamical characterization in QCL, explore the mechanism of the generation of nonlinear dynamical properties of QCL, and summarize the applications of nonlinear properties of QCL.

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    • Design of the integrated interaction circuits for a 200-kW Ka-band klystron with two output ports

      2023, 42(6):771-778. DOI: 10.11972/j.issn.1001-9014.2023.06.010

      Abstract (148) HTML (60) PDF 1.33 M (682) Comment (0) Favorites

      Abstract:In this paper, an efficient resonant circuit based on integrated interaction units is proposed to improve the beam-wave interaction for increasing the peak power of a Ka-band klystron to 200 kW. The integrated-unit circuit is designed with connecting two or several single-beam-wave interaction units across the cross section (each of which is typically used in a conventional single-beam klystron) based on the cascaded field structure in the rectangular gap waveguide with specific fusion boundary conditions. For the input cavity, two interaction units have been efficiently integrated to obtain the optimal absorption efficiency with the constant input power at ~35 GHz, through optimizing both the beam-loading parameters and cavity parameters. The output cavity has been 1) designed with two output ports for balancing the effect of the power extraction on the integrated circuit, and 2) optimized to deliver 200-kW peak power through injecting two pre-modulated beams. The overall interaction circuit of a Ka-band klystron is accordingly designed to produce the peak power of 202.9-kW with the efficiency of 40.2% and the maximum gain of 47 dB using particle-in-cell (PIC) simulations, when the two beams with the voltage of 45 kV and every current of 5.6 A are used to drive the klystron.

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    • Enhanced terahertz wave generation in air-plasma induced by femtosecond three-color harmonic pulses

      2023, 42(6):779-787. DOI: 10.11972/j.issn.1001-9014.2023.06.011

      Abstract (160) HTML (38) PDF 1.21 M (858) Comment (0) Favorites

      Abstract:The generation of terahertz waves from air-plasma induced by femtosecond three-color harmonic pulses with a frequency ratio of 1:2:mm is a positive integer), based on the transient photocurrent model and the sawtooth-like electric field formed via multi-color harmonic pulses superposition, has been theoretically investigated. It can be seen that when the air is saturated ionized and the electron density reaches the same maximum, for the same number of harmonic pulses, terahertz conversion efficiency is not always higher when the electric field shape in the composed pulse envelope is closer to a sawtooth waveform and more asymmetric. Besides, the specific wavelength combination schemes of femtosecond three-color harmonic pulses with the frequency ratios of 1:2:3 and 1:2:4 have also been simulated, which can significantly enhance the generation of terahertz waves, and are realized by adding only a set of optical parametric amplifiers on the basis of the conventional two-color laser pulse case at the frequency ratio of 1:2. Our study will be helpful to obtain intense terahertz sources and provide guidance for experimental operations.

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    • From terahertz to mid-infrared ultra-broadband radiation generated from few-cycle laser pulse interaction with gas plasma filament

      2023, 42(6):788-794. DOI: 10.11972/j.issn.1001-9014.2023.06.012

      Abstract (144) HTML (47) PDF 1.75 M (743) Comment (0) Favorites

      Abstract:The strong few-cycle laser pulse interaction with the gas plasma filament can generate strong and broadband terahertz radiation. Here, we investigate the detail of plasma current and its terahertz radiation produced by the few-cycle laser pulse interaction with the gas plasma based on the calculations. The ionization during the plasma filamentation is in the transition between the tunnel ionization and the multiphoton ionization. The results show that this scheme can generate ultra-broadband radiation from the range of terahertz to mid-infrared, and its amplitude is a periodic function of the carrier-envelope phase of the few-cycle laser pulse. The frequency of the terahertz pulse is determined by the duration of the laser pulse, the time evolution of ionization and the plasma current, rather than by the density of the plasma. This work might give a useful clue to carry out the experiment of ultra-broadband terahertz generation by the few-cycle laser pulse interaction with the gas plasma filament.

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    • Single mode terahertz quantum cascade lasers based on distributed Bragg reflector

      2023, 42(6):795-805. DOI: 10.11972/j.issn.1001-9014.2023.06.013

      Abstract (180) HTML (55) PDF 1.72 M (785) Comment (0) Favorites

      Abstract:In the conventional semiconductor distributed Bragg reflector (DBR) lasers, to obtain stable single mode emission, the gain section should be short enough to make the free spectrum range larger than half of the bandwidth of the reflection plateau caused by the DBR. This constraint severely limits the threshold and the output power of the lasers. In this work, single mode terahertz DBR quantum cascade lasers (THz-DBR-QCLs) that break the above constraint are realized. The lasers are based on the ridge waveguide, and exploit a cleaved facet and a DBR mirror to construct the resonator. Exploiting the intrinsic narrow gain spectrum of the THz-QCL, we tailor the reflection spectrum of the DBR so that the high reflection plateau and the gain spectrum are partially overlapped, obtaining the THz-QCLs with single mode emission. Such strategy enables single mode emission with a significantly elongated gain section, far beyond the constraint of the free spectrum range. In experiments, we realize the single mode THz-DBR-QCLs, whose gain section is as long as 3.6 mm. The emission frequency is about 2.7 THz, and the side mode suppression ratio (SMSR) exceeds 25 dB. The measured threshold and temperature characteristics of the THz-DBR-QCLs are comparable to the Fabry-Perot THz-QCLs fabricated with the same material. Our work suggests a novel approach to realize the high performance single mode THz-QCLs.

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    • A review on Terahertz lens antennas

      2023, 42(6):806-814. DOI: 10.11972/j.issn.1001-9014.2023.06.014

      Abstract (267) HTML (108) PDF 1.21 M (1033) Comment (0) Favorites

      Abstract:The terahertz (THz) antenna is an indispensable component of the future 6G mobile communication, among which the THz lens antenna has attracted extensive attention due to the merits of high gain, stable radiation performances, low cost etc. THz lens antennas can operate without suffering from the problem of feeding occlusion, they can also realize the functions of beam control. The function of focusing can not only be applied in the imaging system, but also play the role of collimation in the test devices. The advancement of THz fabrication technology makes the THz lens antenna more precise and effective, which further promotes the development of the THz lens antenna. In this review, the THz lens antennas reported in the last five years are summarized by synthesizing their features such as functions, fabrication processes, morphologies, and applications.

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    • >Infrared Spectroscopy and Spectral Analysis
    • Novel local calibration optimization from soil mid-infrared spectral library

      2023, 42(6):815-823. DOI: 10.11972/j.issn.1001-9014.2023.06.015

      Abstract (163) HTML (68) PDF 2.33 M (745) Comment (0) Favorites

      Abstract:Soil mid-infrared (MIR) can provide a rapid, non-polluting, and cost-efficient method for estimating soil properties, such as soil organic carbon (SOC). Although there is a wide interest in using the soil spectral library (SSL) for soil analysis at various scales, the SSL with a general calibration often produces poor predictions at local scales. Therefore, developing methods to ‘localize’ the spectroscopic modelling is a reliable way to improve the use of SSL. In this study, we proposed a new approach that aims to rapidly build the optimal local model from the SSL by calculating the spectral similarity and developing the local calibration, in order to further improve the prediction accuracy. The distance matrix was constructed by three distance algorithms, namely Euclidean distance, Mahalanobis distance, and Cosine distance, which were compared and used to measure the similarity between the local samples and the SSL. The capacity curve, which was taken from the distance matrix, was used with a method called “continuum-removal” to find the feature points. Partial least-squares regression was used to build the spectroscopic models for SOC estimation. We found that for all three distance algorithms combined with the continuum-removal, the local calibration derived from the first feature point gave us a good idea of how accurate the prediction would be. The Mahalanobis distance can effectively develop the optimal local calibration from the MIR SSL, which not only achieved the best accuracy (R2 = 0.764, RMSE = 1.021%) but also used the least number of samples from SSL (14% SSL). On local scales, the approach we proposed can significantly improve both the analytical cost and the accuracy of the soil MIR technique.

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    • Research on hyperspectral image classification method based on deep learning

      2023, 42(6):824-832. DOI: 10.11972/j.issn.1001-9014.2023.06.016

      Abstract (228) HTML (107) PDF 1.14 M (937) Comment (0) Favorites

      Abstract:Targeting the issue of insufficient accuracy of hyperspectral image classification methods, a hyperspectral image classification method based on Spatial-spatial transformer (SST) network is proposed. Firstly, the hyperspectral images are preprocessed into one-dimensional feature vectors. Then, the SST hyperspectral image classification network with spectral-spatial attention module and pooled residual module is designed. The overall classification accuracy of the proposed classification method on Indian Pines dataset and Pavia University dataset is 98.67% and 99.87%, respectively, which indicates that this method has high classification accuracy and provides a new scheme for hyperspectral image classification and application.

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    • Evaluation of observation quality of FY-3E/HIRAS-II using the innovation vector method

      2023, 42(6):833-842. DOI: 10.11972/j.issn.1001-9014.2023.06.017

      Abstract (210) HTML (77) PDF 2.27 M (837) Comment (0) Favorites

      Abstract:FY-3E/HIRAS-II is the first early mooring orbiting infrared hyperspectral instrument in the world. Evaluating the quality of its observation data plays a very important role in improving the data assimilation and the accuracy of global numerical weather prediction. Based on the 35 days of HIRAS-II observations from December 2021 to January 2022 and March 2022, this paper uses the innovation vector method to assess the quality of the on-orbit observation data. The distribution characteristics of O-B deviation and standard deviation are calculated by land and ocean respectively. Further matching MetOp-B/IASI observation data in the same time period and in the same region, the double-difference method is used to analyze the quality of HIRAS-II observation data, which can eliminate the influence of radiation transfer mode simulation deviation. The results show that the O-B average deviation of long wave and medium wave in most channels is less than 0.5 K, and the standard deviation is within 1 K. The standard deviation on land is larger than that on ocean (especially for window channels). Due to the deviation of ERA5 reanalysis data, the radiation value simulated by RTTOV has a systematic error in the 664-665 cm-1 CO2 absorption band and the 1 300-1 680 cm-1 water vapor absorption band, which makes the deviation larger, and the double O-B bias in these bands compared with MetOp-B/IASI is close to 0 K, indicating that the O-B bias is mainly caused by the simulation error of the radiation transfer mode, rather than the low quality of the instrument observation. The large deviation near the 980-1 080 cm-1 O3 absorption band and the 1 300 cm-1 CH4 absorption band is caused by the use of fixed climate profile values in RTTOV. The O-B average deviation of short wave in most channels is between -2 K and 2 K, and the standard deviation is within 2 K. The channels near 1 920 cm-1 are the junction of medium wave and short wave of the instrument, so different detectors will cause large O-B deviation. The large deviation of 2 267-2 380 cm-1 due to the fact of the NLTE effect (Non-local Thermodynamic Equilibrium) is not taken into account when RTTOV simulates the brightness temperature. The deviation and standard deviation of channels greater than 2 400 cm-1 increase gradually due to solar pollution. HIRAS-II O-B deviation is asymmetric with the scanning angle, so it is necessary to correct the scanning angle deviation when using HIRAS-II data.

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    • >Remote Sensing Technology and Application
    • An infrared zoom imaging system with large zoom ratio based on linear motion mechanism

      2023, 42(6):843-850. DOI: 10.11972/j.issn.1001-9014.2023.06.018

      Abstract (145) HTML (44) PDF 1.91 M (722) Comment (0) Favorites

      Abstract:In order to meet the urgent need of large-scale search and accurate target recognition, an infrared zoom imaging system with large zoom ratio is developed. Two independently moving zoom lenses and one compensating lens are designed, the large zoom ratio can be obtained by the cascade of two zoom lenses. According to the characteristics of multiple moving lenses and complex zoom curves, the zoom motion is realized by linear motion mechanism, and driven by linear motor integrated encoder and thread screw rod. The mechanical analysis of the system is carried out by the finite element simulation, and the maximum displacement of the lenses is 3.04×10-3 mm. The imaging system is suitable for the medium-wave infrared cooled 640×512 focal plane area-array detector, and the zoom ratio is 55. The results of laboratory imaging and outfield imaging show that the system has a clear and good imaging quality with a continuous change in focal length from 6 mm to 330 mm, which verifies the performance of the system. The design is reasonable and reliable. The research findings of this paper have broad application prospects in search, tracking, reconnaissance, and surveillance.

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    • A self-calibration method of the boresight angles of airborne hyperspectral VNIR/SWIR modules

      2023, 42(6):851-862. DOI: 10.11972/j.issn.1001-9014.2023.06.019

      Abstract (162) HTML (69) PDF 4.15 M (769) Comment (0) Favorites

      Abstract:External field-of-view (FOV) stitching is an effective way to achieve an airborne hyperspectral imaging system with both a large field-of-view and a wide spectral sampling range. However, due to the independent installation of each module, the boresight angles between the corresponding VNIR module and SWIR module will change after a long period of equipment operation, and the change of boresight angles will negatively affect the data fusion effect. The overlap of FOV makes the calibration method based on the epipolar geometry and homography constraints ineffective in solving the boresight angles between the corresponding VNIR/SWIR modules. In this paper, an algorithm based on the reprojection error is proposed for an airborne hyperspectral imaging system with external field-of-view stitching to achieve self-calibration of the boresight angles and focal length between the VNIR/SWIR backends. The algorithm has been applied to the Airborne Multi-Modality Imaging Spectrometer (AMMIS). Experimental results show that the average error of the method is less than 0.2 pixels, and it is also well adapted to tilt-placed modules.

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    • >Infrared Photoelectric Technology and Application
    • The photon detection mode and performance analysis of SiPM photon counting Lidar under different discrimination thresholds

      2023, 42(6):863-873. DOI: 10.11972/j.issn.1001-9014.2023.06.020

      Abstract (165) HTML (114) PDF 2.23 M (861) Comment (0) Favorites

      Abstract:Silicon photomultiplier (SiPM)is a silicon array structure based on the Geiger mode avalanche photodiode. It not only has extremely high photon counting sensitivity and response speed, but also has the characteristics of high dynamic range and linear response under the multi-photon condition, which makes it have unique advantages in the application of photon counting LIDAR. However, due to the multi-pixel, single-time channel working mode of SiPM, its output voltage has a greater probability of pulse pile up compared with other single-photon detectors. Therefore, the detection process of SiPM under different discrimination thresholds is more complicated. To solve this problem, a SiPM photon event response model is established in this paper. Based on this, the time-domain distributions of the shielding effect and the triggering effect caused by pulse pile up are discussed. Finally, the semi-analytic detection probability and false alarm probability models of SiPM are established. At the same time, a photon counting Lidar system based on SiPM detector is built, and the theoretical model is verified by observing that the measured output voltage waveform and point cloud distribution are consistent with the theoretical model (R2>0.95). Furthermore, the distribution of SiPM photon point cloud with different discrimination thresholds is quantitatively evaluated by the recall and precision ratio, and the optimal discrimination threshold interval is given, which has important guiding significance for the design and theoretical analysis of photon counting Lidar system based on SiPM.

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    • Analysis of the operating distance of infrared polarimetric imaging system considering the non-ideality of the detector

      2023, 42(6):874-882. DOI: 10.11972/j.issn.1001-9014.2023.06.021

      Abstract (169) HTML (63) PDF 897.62 K (822) Comment (0) Favorites

      Abstract:To compare the detection capabilities of traditional infrared imaging systems and infrared polarization imaging systems, the operating distance models of the systems were established based on the minimum resolvable temperature difference and the minimum resolvable polarization degree difference. The effects of parameters of non-ideal detectors on the detection capabilities of the systems were discussed, and the corresponding experiments were designed to verify the reliability of the established models. This provides a reference for the selection of imaging systems in different application scenarios in actual detection.

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    • A 0.3 W@4.2 K high-capacity lightweight cryogenic system for space BIB detection

      2023, 42(6):883-894. DOI: 10.11972/j.issn.1001-9014.2023.06.022

      Abstract (188) HTML (44) PDF 1.72 M (744) Comment (0) Favorites

      Abstract:Large-array BIB detectors have been the subject of extensive research due to their high quantum efficiency and low dark current, particularly for space applications such as the JWST, which was launched in 2021 and has made numerous significant astronomical observations. A stable, efficient, and lightweight temperature zone liquid helium cryogenic system is essential to the operation of the BIB detectors. The helium JT cryocooler is a trend that aims to meet the cooling requirements of a liquid helium temperature zone in space while supplanting the traditional, large-volume liquid helium dewar. To simultaneously increase the cooling capacity at 4.2 K and reduce its weight, a high-capacity, lightweight 4.2 K cryocooler with a cooling power of 0.3 W@4.2 K is proposed. Experiments on the previous 0.1 W at 4.1 K prototype of the cryogenic system have validated the system''s design method. Different cooling methods are used in different cooling temperature zones to achieve the efficiency and lightness of cooling. A new integrated Stirling cryocooler was developed to provide efficient pre-cooling at 80 K, with a cooling capacity of 15 W and a weight of only 4.5 kg. A 0.9 W at 15 K active piston phase-shifting pulse tube cryocooler is used to improve the efficiency of the second-stage pre-cooling. The developing cryogenic system can provide a cooling capacity of 0.3 W at 4.2 K with a power consumption of less than 1.8 kW by coupling the helium JT cycle. It will provide the essential guarantee for the large-scale BIB detection required for infrared astronomical observation, which is undergoing rapid development.

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    • Clinical research progress on the fluorescence imaging in the second near-infrared window

      2023, 42(6):895-905. DOI: 10.11972/j.issn.1001-9014.2023.06.023

      Abstract (226) HTML (87) PDF 1.69 M (918) Comment (0) Favorites

      Abstract:The near-infrared fluorescence imaging is a vital technology that enables the image-guided surgery. In recent years, the maturation of the optical bioimaging theory in the second near-infrared window (NIR-II, 900-1 700 nm) has led to the emergence of NIR-II fluorescence imaging as a significant research area in the imaging-guided surgery. This paper provides a succinct overview on the current development state of NIR-II fluorescence probes and imaging systems based on the NIR-II optical bioimaging theory. Furthermore, it reviews the studies conducted on the NIR-II fluorescence imaging in the small animal and clinical surgery, and discusses the potential and challenges of this technology in the clinical surgery, including the difficulties that need to be addressed in the future clinical translation.

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    • >Image Processing and Software Simulation
    • Depth estimation of thermal infrared images based on self-supervised learning

      2023, 42(6):906-915. DOI: 10.11972/j.issn.1001-9014.2023.06.024

      Abstract (162) HTML (95) PDF 1.11 M (762) Comment (0) Favorites

      Abstract:Depth estimation based on unsupervised learning is one of the important issues in the field of computer vision. However, existing algorithms of depth estimation are mainly designed based on visible images. Compared with visible images, thermal infrared images have the disadvantages of low contrast and insufficient detailed information. To this end, a depth estimation network is constructed and an unsupervised depth estimation method is proposed for thermal infrared images according to their characteristics. The network consists of three parts: feature extraction module, feature aggregation module, and feature fusion module. Firstly, a feature aggregation module is designed to improve network ability to acquire the edge information of target objects and the small object information of the image. Secondly, the channel attention mechanism is introduced in feature fusion module to effectively capture the interaction relationship between different channels. Finally, a depth estimation network for thermal infrared images is established. In this network, the model parameters are trained by thermal infrared sequence images to achieve the pixel-level depth estimation of a single thermal infrared image. The results of ablation studies and comparative experiments fully demonstrate that the performance of the proposed method in pixel-level depth estimation of thermal infrared image outperforms other representative methods.

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    • An unsupervised few-shot infrared aerial object recognition network based on deep-shallow learning graph model

      2023, 42(6):916-923. DOI: 10.11972/j.issn.1001-9014.2023.06.025

      Abstract (193) HTML (71) PDF 3.63 M (803) Comment (0) Favorites

      Abstract:In the field of military aerial object recognition, due to the lack of samples, current artificial intelligence algorithms cannot perform well. This paper uses the existing sufficient auxiliary domain images to assist the application domain with few samples for cross-domain object recognition and solves the problem of weak generalization ability and poor performance of the recognition model caused by missing labels and sparse samples. A cross-domain object recognition algorithm named Deep-Shallow Learning Graph Model (D-SLGM) is proposed. Firstly, a deep-shallow two-stream feature extraction algorithm is proposed to solve the problem of feature representation under unsupervised few-shot conditions. At the same time, a feature fusion algorithm based on graph model is proposed to realize high precision fusion between features. Then, a recognition model is trained based on the fused features, the generalization ability of the algorithm is improved. The self-built aerial object dataset is adopted with three application scenarios. The experimental results show that the mean average recognition accuracy of D-SLGM reaches 78.2%, which is better than those of the comparison methods. D-SLGM has great potential in actual aerial object recognition applications.

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    • A whole chain automatic simulation method for the on-orbit stray light effect of optical payloads

      2023, 42(6):924-930. DOI: 10.11972/j.issn.1001-9014.2023.06.026

      Abstract (169) HTML (51) PDF 1.29 M (796) Comment (0) Favorites

      Abstract:The temperature inversion inconsistency phenomenon is analyzed for the on-orbit IR calibration of Visible and InfraRed Radiometer (VIRR) which is a payload onboard polar-orbiting meteorological satellite FY-3C. A specific methodology, i.e., the whole chain automatic simulation and analysis, is proposed. This method involves the orbital parameters and the satellite platform environment. By means of the ray trace of the opto-mechanical structure with high precision, the quantified effect of solar stray light is obtained. The simulation includes on-orbit IR calibration and solar incidence, resulting in the identification of the incidence path of solar stray light as well as the explanation for the temperature inversion inconsistency. Through the comparison between the simulated results and the on-orbit data of the satellite, the effectiveness and the validity of the method are verified. This method can be applied to the simulation and analysis of on-orbit stray light effect of the same-typed payloads. This work can also provide references to the recalibration of historical data.

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    • Coronene enhanced CMOS image sensor

      2023, 42(6):931-936. DOI: 10.11972/j.issn.1001-9014.2023.06.027

      Abstract (143) HTML (81) PDF 1.30 M (894) Comment (0) Favorites

      Abstract:The responsiveness of typical silicon-based CMOS image sensors in the UV band is not high due to the limited penetration depth of UV light in silicon and the absorption of UV light by poly silicon gates. A low-cost down-conversion method was used in this work to enhance the UV response of a CMOS image sensor. Vacuum thermal evaporation was used to deposit coronene films on quartz substrates and CMOS image sensors, respectively. The films'' optical characteristics,infrared spectrum,light stability,and thermal stability were investigated. The experimental results reveal that the Coronene coating absorbs UV light and emits green fluorescence at 500 nm,which closely matches the spectral response peak of the CMOS image sensor. At the same time,it is found that the experimental value of the infrared absorption spectrum of Coronene is in good agreement with the calculated value,and the fluorescence intensity of the emission peak remained 95.7% after the film was annealed at 200 ℃ for 20 minutes. After approximately 60 minutes of exposure at 280 nm excitation wavelength,the fluorescence intensity decreased exponentially to 64% of the initial value. The UV enhancement effect of the film was qualitatively analyzed by the CMOS monochromatic camera under visible light(400-780 nm) and ultraviolet light (365 nm) radiation. It is found that the sensitivity of the CMOS monochromatic camera to UV light can be improved after the deposition of Coronene film.

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Editor in chief:Jun-Hao CHU

International standard number:ISSN 1001-9014

Unified domestic issue:CN 31-1577

Domestic postal code:4-335

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