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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2022, 41(1):15-39. DOI: 10.11972/j.issn.1001-9014.2022.01.001
Abstract:Infrared photon detection technology usually works in the passive sensing mode and contains the advantages of long acting-distance， good anti-interference， excellent penetration of smoke and haze， and all-day operation， which has been widely used in space remote sensing， military equipment， astronomical detection and other aspects. So far， the second-generation and the third-generation infrared photon detectors have been deployed widely. The high-end third-generation infrared photon detectors have been gradually promoted to practical application. The fourth generation and more forward-looking research including new concept， new technology， and new device has been proposed. This paper focuses on the research status of infrared technology at home and abroad， emphatically introducing the hotspots and development trends of infrared photon detectors. Firstly， the concept of SWaP3 is introduced due to tactical ubiquity and strategic high performance. Secondly， the high-end third-generation infrared photon detectors with ultra-high spatial resolution， ultra-high energy resolution， ultra-high time resolution and ultra-high spectral resolution are reviewed. Technical characteristics and implementation methods of ultimate-performance infrared detectors are analyzed. Then， the fourth-generation infrared photon detector based on the artificial micro-structure is discussed. The realization approaches and technical challenges of multi-dimensional information fusion such as polarization， spectrum and phase are mainly introduced. Lastly， highly innovative trends of future detectors are discussed according to upgradation from on-chip digitization to on-chip intelligence.
2022, 41(1):40-60. DOI: 10.11972/j.issn.1001-9014.2022.01.002
Abstract:The infrared photodetector can obtain IR radiation either reflected by or radiated from the target， which is a unique property and makes infrared photodetectors play an important role in areas such as national defense， communications， remote sensing， and aerospace along with other advantages， such as strong anti-interference， full-time detection， long detection range， and high-resolution imaging. The infrared photodetector is undergoing radical development from the application of the first generation multielement detectors in the 1940s to the striving for the proposal of SWaP3 concepts in the third generation in the late 1990s. Traditional infrared photodetectors， of which the advancement focus on improving performance indicators such as array size， sensitivity， and resolution， using light intensity information for imaging， are sluggish to meet future demanding such as recognizing diverse targets， facing environmental complexity， and dealing with multiform tasks at the same time. Infrared photodetectors for multidimensional optical information acquisition provide new routes to improve the device performance and meet future needs. Infrared photodetector obtains not only abundant intrinsic information of light besides intensity， such as phase， wavelength， polarization， and momentum， but also external information like optical path. This paper focuses on the multi-dimension infrared detection extracting information of wavelength， polarization， phase， and the optical path of the targets， which does not only summarize the research progress of infrared photodetectors from the aspects of new principles， new materials， and new structures， but also put forward the idea and outlook for the development direction of the multi-dimensional infrared photodetectors.
2022, 41(1):61-73. DOI: 10.11972/j.issn.1001-9014.2022.01.003
Abstract:Various types of electromagnetic radiation can be stimulated by free electrons interact with the local electromagnetic environment. Metamaterial is a kind of artificial material， which can achieve unique characteristics that natural material cannot realize. Based on the interaction between the metamaterial and free electron， the radiation characteristics can be flexibly manipulated such as polarization， phase and wavefront， and so on. The related study provides a novel platform for developing novel free-electron radiation devices. This paper briefly introduces the physical mechanism of Cherenkov radiation and Smith-Purcell radiation. Then， the state-of-art of free-electron radiation in metamaterials is introduced. Finally， an outlook of potential research directions for this vigorous realm is provided.
2022, 41(1):74-84. DOI: 10.11972/j.issn.1001-9014.2022.01.004
Abstract:Spectral instruments have the ability to acquire spectral information and images for targets， and can realize nondestructive identification and quantitative interpretation of the mineral composition， which has become the key scientific payloads in lunar and Mars exploration missions， and provides an important basis for the study in aspects of surface composition and mineral resources， formation and evolution history and resource utilization. This paper briefly illustrates the research progress and application status of spectroscopic technology in lunar and Mars exploration missions at the domestic and international level in recent years. The seven spectral instruments and their application status in China’s Lunar Exploration Program （CLEP） and Tianwen-1 mission are summarized. In addition， this paper further introduces the typical scientific outputs for lunar and Martian spectral data. Finally， the application prospect and development trend of spectral instruments in the field of lunar and deep space exploration are discussed.
2022, 41(1):85-102. DOI: 10.11972/j.issn.1001-9014.2022.01.005
Abstract:The terahertz wave has great potential in deep space exploration， nondestructive testing， communication and security inspection because of its characteristics of electronics and photonics. The rapid development of terahertz technology in recent years is inseparable from the continuous progress of terahertz vacuum electronic devices. Due to the size sharing effect and the limitation of electron beam emission performance， this type of device has encountered considerable difficulty in the process of higher frequency bands. To solve these problems， a series of measures have been taken， such as improving high-frequency structure， controlling machining accuracy， preparing materials with better performance and more accurate calculation methods. This paper introduces the solutions and the latest progress of several mainstream miniaturized terahertz devices， and finally summarizes the problems and solutions that may be encountered in the future according to the current development situation.
2022, 41(1):103-109. DOI: 10.11972/j.issn.1001-9014.2022.01.006
Abstract:Terahertz quantum well photodetectors （THz QWPs） are ultra-fast devices， which have picosecond response time and more than 1 GHz modulation speed. THz QWPs have great potential applications in the field of THz fast imaging and high-speed wireless communications. This paper summarizes the principle， design， performance and recent research progress of THz QWPs. Research shows that the fast imaging system based on THz QWPs can detect the detailed information of the object， which is expected to be used in the field of safety inspection and nondestructive testing. Additionally， THz QWPs can be used as the detection end of high-speed wireless communication， providing an effective technical approach for future 6G wireless communications.
2022, 41(1):110-121. DOI: 10.11972/j.issn.1001-9014.2022.01.007
Abstract:Airborne infrared remote sensing technology has irreplaceable advantages， such as full-time work， flexibility and high spatial resolution， etc. It plays a key role in remote sensing science， land monitoring， national defense applications， etc. Development of airborne infrared remote sensing is vital to our country''s national defense and economic development. In recent years， airborne infrared remote sensing technology has developed rapidly， with crucial breakthroughs in high spectral resolution infrared imaging and high spatial resolution infrared imaging. To get higher spatial resolution， spectral resolution， temporal resolution and radiometric resolution are missions of infrared technology research group. While introducing the latest international developments， the paper presents significant technological breakthroughs made by the Shanghai Institute of Technical Physics airborne remote sensing team in full-spectrum hyperspectral imaging and area-array scanning imaging. New generation instruments have been successfully applied to land classification， thermal drainage monitoring of nuclear power plants and other application fields. The latest results are given.
2022, 41(1):122-128. DOI: 10.11972/j.issn.1001-9014.2022.01.008
Abstract:High operating temperature infrared detector is one of the important development tendencies for the third-generation infrared focal plane. The interband cascade photodetectors take advantage of potential barrier structure and multistage absorption structure. Unidirectional transport of photogenerated carriers is achieved through relaxation and tunneling region which can reduce the generation-recombination current from the depletion region of the PN junction. The interband cascade detectors can effectively collect photo-generated carriers， and even the diffusion length is short utilizing the multiple and short absorption regions. So the detection performance can be improved at high operating temperature. In this paper， we present our recent research progress in the interband cascaded infrared optoelectronic devices， including high operation temperature infrared interband cascade detectors， high speed interband cascade detectors， and interband cascade light-emitting devices.
2022, 41(1):129-138. DOI: 10.11972/j.issn.1001-9014.2022.01.009
Abstract:To meet with the ongoing demand for the development of higher performance space remote sensing instruments， a series of progress in short wavelength infrared InGaAs focal plane arrays （FPAs） has been achieved in Shanghai Institute of Technical Physics. Through the continuous research efforts devoted to the low-defect density epitaxial materials， the FPA processing technologies as well as the low noise read-out circuits， a 10-μm-pitch 1~1.7 μm InGaAs FPA with an array format up to 2560×2048， a pixel operability up to 99.7% and a high peak detectivity up to 1.1×1013 cmHz1/2/W is realized. A 15-μm-pitch 1~2.5 μm extended wavelength InGaAs FPA with an array format of 1280×1024 and a high peak detectivity up to 5.0×1011 cmHz1/2/W is also achieved. New principle FPA detectors are also developed， which are a monolithic integrated four-direction polarized 160×128 InGaAs FPA with a high extinction ratio up to 37：1， and a 64×64 InGaAs Geiger-mode avalanche FPA with a fine timing resolution down to 0.8 ns.
2022, 41(1):139-150. DOI: 10.11972/j.issn.1001-9014.2022.01.010
Abstract:The nBn infrared （IR） detector is designed to eliminate the Shockley-Read-Hall （SRH） generation-recombination （G-R） currents， which will effectively reduce the dark current and increase the operating temperature of the detector. Due to the compatibility of the manufacturing process and the existence of a substrate with a perfectly matched lattice， the nBn infrared detectors based on III-V compounds including type-II superlattice （T2SLs） materials have been developed rapidly. Through theoretical simulation， the nBn infrared detector based on the HgCdTe material system can also effectively suppress the dark current. However， the difficulty of removing the valence band barrier hinders HgCdTe nBn infrared detector development. This review will elaborate on the physical mechanism of nBn detectors to suppress dark current， and then introduce the development status and development trend of nBn barrier detectors in different semiconductor materials.
2022, 41(1):151-168. DOI: 10.11972/j.issn.1001-9014.2022.01.011
Abstract:Subwavelength thin-film stack metamaterials， as a special group of metamaterials， have attracted much attention owing to their subwavelength thickness， ease of fabrication， low-cost and large-area fabrication capacities， etc. In this article， the recent research progress of the theory and applications based on subwavelength thin-film stack metamaterials is reviewed. We first focus on the overview of the theoretical background and the newly developed techniques for subwavelength thin-film stack metamaterials. Then， we highlight the progress of recent applications， including structural colors， photoluminescence （PL） enhancement， thermal emitter and infrared stealth， etc. Finally， the future opportunities and challenges about further research on the subwavelength thin-film stack metamaterials are also addressed.
2022, 41(1):169-180. DOI: 10.11972/j.issn.1001-9014.2022.01.012
Abstract:As one of the most effective methods to generate terahertz laser， how to improve the performance of terahertz quantum cascade laser has been the focus of the scientific community. In this review， the current performance of terahertz quantum cascade lasers is described from the perspective of photonic and electric control. Starting from the principle of active region design of laser， several new active region designs are introduced， and then a series of new structures are introduced from the perspective of resonator， and their improvement on power and beam quality is shown. Finally， we describe the recent progress in polarization regulation and frequency tuning of terahertz quantum cascade lasers.
2022, 41(1):181-198. DOI: 10.11972/j.issn.1001-9014.2022.01.013
Abstract:The wide-field fluorescence microscopic imaging in the second near-infrared region （NIR-II， 900-1880 nm） is currently a hot spot for deep in vivo bioimaging， with great potential in both basic research and clinical applications. Compared to the visible （Vis， 360-760 nm） and the first near-infrared （NIR-I， 760-900 nm） region， NIR-II fluorescence in vivo wide-field microscopic imaging provides higher spatial resolution and deeper tissue penetration. On the basis of NIR-II macroscopic imaging， the demand for deciphering of tissue microstructure forces the continuous development of fluorescent agents and the imaging system. NIR-II wide-field microscopic imaging technology has achieved a series of breakthroughs in biological applications such as accurate vascular microscopy， tumor analysis and accurate inflammation tracking. The research objects include rodents （such as mice and rats） and non-human primates （such as marmosets and macaques）. With the breakthrough of instrument commercialization and localization as well as the increasing biocompatibility of fluorescent probes in the future， the application values of NIR-II fluorescence wide-field microscopic imaging will continue to upsurge. This article discusses the mechanism and advantages of NIR-II imaging first，and then， reviews the characteristics and history of NIR-II fluorescence wide-field microscopic imaging， as well as its latest exploration and prospects for in vivo imaging on different biological models. The purpose is to promote the further popularization of NIR-II fluorescence in vivo wide-field microscopic imaging.
2022, 41(1):199-209. DOI: 10.11972/j.issn.1001-9014.2022.01.014
Abstract:In order to solve the problems of image quality evaluation， imaging link analysis and subsequent processing algorithm verification due to the lack of in-orbit data before satellite launch， an in-orbit geometric imaging simulation method for long-linear-array and whisk-broom （LLAWB） thermal infrared imager （TIRI） based on ray tracing is proposed. Firstly， according to the structure and imaging characteristics of the optical system， the rigorous geometric imaging model of the LLAWB TIRI is constructed. Then， based on the simulation attitude and orbit parameters， auxiliary DOM and DEM data， the spatial projection and imaging simulation of pixel visual vector are realized by ray tracing and re-projection algorithm. Finally， a geometric calibration method based on "generalized" correction matrix is proposed to modify the positioning model and improve the positioning accuracy of simulation images. Experimental results show that the proposed method can be used to simulate the geometric imaging of any orbit position for the LLAWB TIRI， and the positioning accuracy of the simulation image is better than two pixels after calibration. This research provides a new idea for in-orbit geometric imaging simulation of space optical payloads， and is of great significance to the error analysis， geometric positioning and calibration of imaging links.
2022, 41(1):210-217. DOI: 10.11972/j.issn.1001-9014.2022.01.015
Abstract:Metasurfaces have intrigued great interest among researchers in electromagnetic （EM） engineering field due to the powerful ability of EM manipulation and advantages of low loss， low profile and ease-fabrication. Nevertheless， due to the limitation of the fabrication technology， currently， most of the reported metasurface carpet invisibility cloaks are composed of two-dimensional planar structures. It is still a challenge to achieve conformal metasurface carpet invisibility cloak for an object with arbitrary boundary. Therefore， we designed and demonstrated a conformal metasurface carpet invisibility cloak with arbitrary boundary based on metasurfaces and 3D-printed technology， which breaks the limitation of two-dimensional planar structures and achieves radar stealth for ground object. Both simulated and measured results show that such conformal metasurface invisibility cloak exhibits an excellent stealth performance and sustains performance stability at certain incident angles. Notably， the proposed 3D conformal metasurface invisibility cloak not only promises a wide application prospect in the EM stealth field， but also opens a new way to design EM devices.
2022, 41(1):218-229. DOI: 10.11972/j.issn.1001-9014.2022.01.016
Abstract:Over the last several years， Terahertz spectroscopy has been used in different fields， including archaeology and cultural heritage conservation. This paper presents a review of the terahertz technology applied to paintings， focusing on THz-TDS （terahertz time domain spectroscopy） in pigment identification， terahertz imaging technology in fresco and oil painting study. Some other new technologies are also discussed.
2022, 41(1):230-247. DOI: 10.11972/j.issn.1001-9014.2022.01.017
Abstract:Radiative cooling has been a hotspot for scientific research recently. As a passive cooling method， it uses outer space as heat sink， and has the advantage of low or even zero energy consumption. It has high potential in many applications such as building air conditioning， solar cell cooling， comfortable clothing， etc. This paper briefly reviews the development history and principles of radiative cooling， systematically introduces the structures and materials of radiative cooling， summarizes the design， preparation and characterization methods of radiative cooling materials， and also summarizes relevant application fields. The future of radiative cooling materials and technology is proposed at the end of this paper.
2022, 41(1):248-252. DOI: 10.11972/j.issn.1001-9014.2022.01.018
Abstract:In this paper， the multi-coatings composed of layers of zinc sulfide and germanium were designed and fabricated on a long-wavelength InAs/GaSb Type-II superlattices infrared focal plane arrays （FPAs）. Compared with the FPAs without multi-coatings， the multi-coatings make the response peaks of the FPAs shift from the wavelength of 8.7 μm and 10.3 μm to that of 9.8 μm and 11.7 μm. The 50% response cut-off wavelength of the FPAs shifts from 11.6 μm to 12.3 μm， and the response intensity of the FPAs is increased by 69% at the wavelength of 12 μm. In summary， the multi-coatings make the response wavelength of the FPAs tunable， which provides a powerful platform for more sensitive long-wave detection and improving imaging capabilities.
2022, 41(1):253-261. DOI: 10.11972/j.issn.1001-9014.2022.01.019
Abstract:InAs/In0.83Al0.17As quantum wells have been demonstrated on In0.83Al0.17As metamorphic layers on GaP/Si substrates. The effects of GaxIn1-xP and GaAsyP1-y graded buffer layers on the sample performances are investigated. The sample with GaxIn1-xP metamorphic buffer layer has narrower width in X-ray diffraction reciprocal space maps， indicating less misfit dislocations in the sample. Mid-infrared photoluminescence signals have been observed for both samples at room temperature， while the sample with GaxIn1-xP metamorphic buffer shows stronger photoluminescence intensity at all temperatures. The results indicate the metamorphic buffers with mixed cations show superior effects for the mid-infrared InAs quantum wells on GaP/Si composite substrates.
2022, 41(1):262-268. DOI: 10.11972/j.issn.1001-9014.2022.01.020
Abstract:Scanning Capacitance Microscopy （SCM） was applied to obtain the 2-dimensional carrier distribution on the cross-section of planar type InGaAs/InAlAs pixels. The profile of pn junction in the device structure was able to be depicted with high space resolution. Besides， for InGaAs/InP detector， the SCM study helps to disclose the distinct diffusion behavior of p-type impurities in different functional layers. The lateral diffusion speed of zinc in InGaAs absorption layer was decided as 3.3 times than that in the depth direction， which is significantly higher than the lateral to depth ratio of 0.67 in the n-InP cap layer， this could affect both the capacitance and dark current properties of the diode pixels.
2022, 41(1):269-278. DOI: 10.11972/j.issn.1001-9014.2022.01.021
Abstract:A novel photonic crystal fiber with high birefringence and low confinement loss is designed， which can be used for chemical sensing . The effects of air holes parameters on optical properties of optical fiber are systematically investigated. The results reveal that the relative sensitivities of the fiber with the optimal structure for water， ethanol and benzene at the wavelength of 1.55 μm are 56.3%， 59.9% and 62.5%， respectively. Compared with the existing PCFs， they are improved by 1.05-6.25 times， 1.05-4.99 times and 1.03-4.63 times， respectively. Besides， it has excellent transmission characteristics. Therefore， the proposed photonic crystal fiber has advantages in chemical sensing and biomedicine filed.
2022, 41(1):279-284. DOI: 10.11972/j.issn.1001-9014.2022.01.022
Abstract:High quality β-Ga2O3-δ films on c-sapphire substrates are deposited by pulsed laser deposition （PLD） under various oxygen partial pressures. The crystalline structure， chemometry and optical properties of the β-Ga2O3-δ films are investigated systematically by X-ray diffraction （XRD）， far-infrared reflectance spectra， X-ray photoelectron spectroscopy （XPS） and ultraviolet-visible-near infrared （UV-vis-NIR） transmittance spectra. The XRD analysis shows that all the as-deposited films are of unique （-201） orientation. The transmittance spectra reveal that the films exhibit a high transparency above 80% in the UV-vis-NIR wavelength region above 255 nm （4.863 eV）. Moreover， the optical constants and optical direct bandgap are extracted based on the transmittance spectra with Tauc-Lorentz （TL） dispersion function model and Tauc’s relationship， respectively. A further step， the influence of oxygen partial pressure on optical properties is explained by theoretical calculation.
2022, 41(1):285-293. DOI: 10.11972/j.issn.1001-9014.2022.01.023
Abstract:In this paper， two millimeter-wave zero-bias Schottky detectors for the direct detection system of the CubeSat radiometer， with center frequencies of 89 GHz and 150 GHz， respectively， were designed and implemented. These designs were based on zero-bias Schottky diodes of ACST. A radial stub structure was adopted at the DC ground and output port with a tuning line for optimum impedance matching to achieve stable and high performance and broadband characteristics； this structure also makes the circuit easier to integrate with pre-level systems and more suitable for CubeSat radiometer miniaturization. Circuit structure and Schottky diode were analyzed， modeled， and optimized to obtain better performance. The results showed that the W-band detector has a typical sensitivity of about 2500 V/W in the range of 85 GHz to 95 GHz and a linearity of 0.9994 at 89 GHz. Moreover， the D-band detector has a typical sensitivity of about 1600 V/W in the range of 145 GHz to 155 GHz and a linearity of 0.9992 at 150 GHz. These results verified the advantages of the improved circuit structure in the detector and the feasibility of the direct detection system.
2022, 41(1):294-298. DOI: 10.11972/j.issn.1001-9014.2022.01.024
Abstract:In this article， an improved millimeter-wave fast imaging algorithm with range compensation for one-stationary bistatic synthetic aperture radar （OS-BiSAR） is presented. During the process of image reconstruction， the amplitude attenuation factor of the echo model is retained for the compensation of signal propagation loss， and the convolution operation is performed on the receiving array dimension according to the characteristics of the target echo equation. Finally， the target image can be solved by fast Fourier transform （FFT） and coherent accumulation steps. Simulation analysis and experimental results show that， compared to the range migration algorithm （RMA） with range compensation， the proposed algorithm can not only guarantee the efficiency of image reconstruction， but also significantly reduce the influence of signal propagation loss on the image quality.
2022, 41(1):299-304. DOI: 10.11972/j.issn.1001-9014.2022.01.025
Abstract:This paper presents the work of a miniaturized 60-GHz balun chip with isolation and matching performance fabricated in 0.18-μm SiGe BiCMOS process. The use of isolation circuit as key building blocks within a 60-GHz transformer balun leads to an improved isolation performance between output ports， while simultaneously achieving the matching performance of them. Moreover， compared to the conventional isolation circuit， the artificial left-handed transmission line is introduced to remove the bulky distributed elements， and the capacitive loading compensation technique is utilized for both matching and miniaturization. Both electromagnetic simulation and measurement results of the proposed 60-GHz transformer balun chip design with isolation and matching characteristics are given with good agreement. From measurement results， better than 25-dB isolation and 18-dB return loss of the output ports have been achieved at 60 GHz， with an occupied area of 0.022 mm2.
2022, 41(1):305-310. DOI: 10.11972/j.issn.1001-9014.2022.01.026
Abstract:A dual-beam rectangular ring-bar （DBRRB） slow wave structure （SWS）， which is with a planar structure and is suitable for micro fabrication， is proposed for W-band traveling-wave tubes （TWT）. Supported by a pair of T-shaped dielectric rods， the RRB SWS is fit for dual-sheet beam operation. The high frequency characteristics are analyzed by using computer simulations. Wide bandwidth input-output structures adopting tapered structure and step waveguide are designed. Hot-test performance of the RRB SWS is investigated by means of Particle-in-cell （PIC） simulations. A solenoid magnetic field of 0.6 T is adopted to focus the sheet beams with voltage and current of 11.2 kV and 0.12 A. The saturated output power of 56.7 W at 94 GHz is obtained at the output port， corresponding a gain of 27.4 dB. In addition， an attenuator is added to suppress oscillations and achieve stable operation.
2022, 41(1):311-316. DOI: 10.11972/j.issn.1001-9014.2022.01.027
Abstract:In this paper， a design， fabrication and cold test of a high efficiency folded groove waveguide （FGW） for w-band （85~110GHz） sheet beam traveling wave tube （TWT） is proposed. One stage phase velocity taper （OSPVT） was used in the FGW to enhance the electronic efficiency of a millimeter-wave sheet beam TWT. The OSPVT was realized via a change of the period of the FGW. Three FGWs with and without OSPVT were fabricated and their measured s-parameters demonstrate good transmission characteristics and wide bandwidth. Moreover， wave dispersions and phase velocities of the unchanged and OSPVT FGWs were obtained from measured transmission phases. 3-D particle-in-cell simulations of beam-wave interaction predicted that the proposed TWT with an OSPVT of twenty half periods could output a saturated power of 240 W at 95 GHz， which is about 70 W higher than the case of without OSPVT. Meanwhile， the application of the OSPVT improves the electronic efficiency in the whole operating frequency range of 85~110 GHz， with a maximum efficiency enhancement of about 47% in the vicinity of 95 GHz.
2022, 41(1):317-322. DOI: 10.11972/j.issn.1001-9014.2022.01.028
Abstract:In this work， excitation power-dependent infrared photoluminescence （PL） measurements were carried out on four GaSb0.93Bi0.07/GaSb single quantum well （SQW） samples with different in-well δ-doping density as well as the corresponding reference SQW samples without doping. PL integral-intensity evolutions of the GaSbBi SQW and the GaSb barrier/substrate show a significant decrease in the infrared emission efficiency caused by the in-well δ-doping. The doping-induced relative decrease rate is about
2022, 41(1):323-336. DOI: 10.11972/j.issn.1001-9014.2022.01.029
Abstract:The suspended sediment concentration （SSC） is an extremely important property for water monitoring. Since machine learning technology has been successfully applied in many domains， we combined the strengths of empirical algorithms and the artificial neural network （ANN） to further improve remote sensing retrieval results. In this study， the neural network calibrator （NNC） based on ANN was proposed to secondarily correct the empirical coarse results from empirical algorithms and generate fine results. A specialized regularization term has been employed in order to prevent overfitting problem in case of the small dataset. Based on the Gaofen-5 （GF-5） hyperspectral remote sensing data and the concurrently collected SSC field measurements in the Yangtze estuarine and coastal waters， we systematically investigated 4 empirical baseline models and evaluated the improvement of accuracy after the calibration of NNC. Two typical applications of NNC models consisting baseline model calibration and temporal calibration have been tested on each baseline models. In both applications， results showed that the calibrated D’Sa model is of highest accuracy. By employing the baseline model calibration， the root mean square error （RMSE） decreased from 0.1495 g/L to 0.1436 g/L， the mean absolute percentage error （MAPE） decreased from 0.7821 to 0.7580 and the coefficient of determination （R2） increased from 0.6805 to 0.6926. After implementation of the temporal calibration， MAPE decreased from 0.8657 to 0.7817 and R2 increased from 0.6688 to 0.7155. Finally， the entire GF-5 hyperspectral images on target date were processed using the NNC calibrated model with the highest accuracy. Our work provides a universal double calibration method to minimize the inherent errors of the baseline models and a moderate improvement of accuracy can be achieved.
2022, 41(1):337-341. DOI: 10.11972/j.issn.1001-9014.2022.01.030
Abstract:Linear and coaxial pulse tube cryocoolers （PTCs） are widely used in space， especially coaxial PTCs. The coaxial PTC has a compact structure and is more convenient to use， while the linear structure is simple with high cooling efficiency. At present， the research on the difference between the two PTCs based on theoretical research is relatively rare. Therefore， it is very valuable to carry out some comparative studies between the two PTCs. Two kinds of Stirling-type single-stage PTCs （in-line and coaxial type） are analyzed due to their different structures in this paper. One-dimensional numerical model is established to analyze the changes of the relevant thermodynamic parameters in the two cryocoolers. The mechanism is revealed that different structural changes could lead to different cooling performance. The differences between the PTCs are compared by analyzing the energy flows， acoustic impedance networks. Also， two experimental setups are established， and the performance of the two pulse tube cryocoolers is tested and analyzed. The results show that the in-line cryocooler has higher cooling efficiency， and the coaxial one could reach lower cooling temperature at the same input power because the pulse tube is placed in the regenerator of the coaxial system and precooled by the regenerator. By comparing the simulation data with the experimental results， it is found that there is a good consistency.
2022, 41(1):342-353. DOI: 10.11972/j.issn.1001-9014.2022.01.031
Abstract:The three elements of water color remote sensing products are chlorophyll， suspended substance and yellow substance. As one of the main loads of HY-1 satellite， Chinese Ocean Color and Temperature Scanner （COCTS） has set up 8 visible and near-infrared detection channels， to provide primary data for the study of global ocean primary productivity distribution. HY-1B COCTS was launched in 2007， and at the beginning of orbit entry there exists light pollution in cold space which works as the zero-radiation datum， which leads to the signal cut-off in the deep-sea area of the near-infrared detection channel， and the lower the latitude， the bigger the cold air signal is. In order to study the mechanism of the problem and repair the historical data of HY-1B COCTS， the characteristics of the source of the problem was verified in the laboratory， and the influence mechanism was analyzed. Based on the relationship between the sun glint energy of HY-1C COCTS and the solar zenith angle， the sun glint energy of HY-1B COCTS at different solar zenith angle is calculated. According to the radiometric calibration coefficient， the corresponding code value of the sun glint energy and the correction quantity can be obtained. The results show that the correction quantity is linear with the energy calculated from the solar zenith angle， and can be used to repair other target signals of HY-1B COCTS. This algorithm can be used to repair the remote sensing data of nearly 9 years of HY-1B COCTS. It lays a theoretical foundation for data comparison between the same kind of ocean remote sensing instrument and retrieving water color products.
2022, 41(1):354-361. DOI: 10.11972/j.issn.1001-9014.2022.01.032
Abstract:It has very important application value to investigate the damage performance of PbS detector irradiated by mid-infrared laser. In this paper， the experiment research on damage in PbS detector irradiated by 2.79 μm mid-infrared laser is carried out. Furthermore， the theoretical model of PbS detector irradiated by 2.79 μm laser is developed and a numerical simulation is performed to calculate temperature distribution in PbS detector using finite element method， and the relationship between laser parameters and damage effect is also studied. The simulation and experimental results indicate that the damage mechanism of PbS detector irradiated by 2.79 μm mid-infrared laser is mainly melting damage， and the melting damage threshold is calculated to be 13.03 J/cm2. Before the temperature reaches the melting point of PbS， the thermal decomposition reaction of PbS begins， and then separates out PbO which is the yellow precipitate. It is shown that pulse repetition frequency and the number of pulses affect damage considerably， and the accumulation of multi-shot laser induced damage in PbS detector is obvious. The theoretical analysis is in agreement with the initial damage morphology of PbS surface.
2022, 41(1):362-369. DOI: 10.11972/j.issn.1001-9014.2022.01.033
Abstract:HgCdTe avalanche photodiode （APD） is the frontier research on infrared focal plane technology. High-precision time stamp''s readout circuit is the basis of the APD focal plane at 77 K， which directly affects APD infrared focal plane performance. Time-to-digital conversion circuit （TDC） is one of the methods to achieve high-precision time stamping. Based on the analysis of MOSFET device at low temperature， we design a vernier TDC circuit， which uses a synchronous counter to quantize an integer multiple of the periods to achieve a coarse count of 6 bits. We use the high-frequency clock multiplied by the on-chip phase-locked loop to quantify the part that is less than one clock cycle to achieve a fine-count of 6 bits output. The circuit adopts standard CMOS process tape out， and our circuit works at a master-frequency of 120 MHz. At 77 K， the circuit tests can distinguish the time resolution of 236.280 ps. The DNL is within -0.54~0.71 LSB， and the INL is within -1.32~1.21 LSB.
Editor in chief：Jun-Hao CHU
International standard number：ISSN 1001-9014
Unified domestic issue：CN 31-1577
Domestic postal code：4-335