This PDF file contains the front matter associated with SPIE Proceedings Volume 12505, including the Title Page, Copyright information, Table of Contents, and Conference Committee Page.

InGaAs/InP single photon avalanche photodiode (SPAD) is important for quantum communication, and LIDAR applications in the near-infrared (NIR) wavelength range, between 0.9 µm and 1.7 µm. Compared with other optoelectronic devices, SPAD has two main advantages: high quantum efficiency and high detection efficiency. In this study, the design and simulating of a separate absorption, grading, charge, and multiplication (SAGCM) structure InGaAs/InP SPAD were conducted by using COMSOL Multiphysics. The electric-field distribution was studied under the given thickness and dopant concentration of each layer of the SPAD. It was found that the edge pre-breakdown of planar-type SPAD resulted from the intense electric field at the junction bend can be prevent from happening by using gaussian type dopant distribution profile. The punch-through voltage and the breakdown voltage were also focused. The results show that the punch-through voltage and the breakdown voltage was 55 V and 65V respectively. In addition, the electric field nonuniformity of the avalanche area increases greatly after the bias voltage exceeded the punch-through voltage.

Through the passive observation and algorithm processing of the two-station infrared camera, the three-dimensional coordinates of the landing point of the shell are located, and the target is automatically reported throughout the day for the range training, which is an important way for training evaluation. The traditional photoelectric imaging target reporting method directly locates the double station based on the detection of the explosion point of the image shell, locates the three-dimensional position of the shell explosion point, and outputs the target reporting results. This method faces two difficulties. Firstly, because the ground in the image cannot provide enough geometric prior knowledge, the detection deviation of the shell explosion point in the image is large, resulting in the target reporting result based on the double station positioning of the shell explosion point cannot meet the 1m accuracy requirement. Secondly, due to the interference of the mushroom cloud at the pre-sequence shell blast point, the explosion point of the group shell is difficult to be effectively detected, so the method does not support the continuous target reporting of multiple bullets. Based on this, this paper proposes a range prediction target reporting algorithm, which is based on the detection of the shell's aerial trajectory for double-station positioning, first locates the three-dimensional track points of the shell target when it moves in the air, then fits out the three-dimensional trajectory of the shell in the air, and finally predicts the three-dimensional position of the shell explosion point based on the bulls eye GPS information, and outputs the target reporting results. The algorithm avoids the detection of image explosion points, which can improve the positioning accuracy of explosion points, and can avoid the interference of mushroom clouds at the explosion points of pre-sequence shells and realize the automatic target reporting of continuous shells. In addition, in view of the problem of matching between group shell stations, this paper adopts the method of multi-target matching target based on track direction estimation. Firstly, it performs single-frame multi-target preliminary matching based on the elevation difference of dual-station direction finding rays and obtains all three-dimensional track points in the air of each shell target. Then, based on the two-dimensional histogram of the direction or the Mean Shift algorithm, the three-dimensional track direction of each shell target is estimated, and the true and false track points are checked based on the three-dimensional track direction of the target, and the false matching points are eliminated. Finally, the three-dimensional trajectory fitting and the position prediction of the explosion point of the shell target are carried out, and the target reporting results are output. Experiments verify that the positioning error of a single shell in this algorithm is 0.57m, and the positioning error of the traditional target reporting algorithm is 1.17m, indicating that even when the shape of the explosion point is regular, the positioning error of the predicted target can be doubled; For the one-shot two-bomb test that can detect the target, the positioning error of the algorithm in this paper is better than 1m, which meets the overall application requirements. In view of the target training of the Yellow Flag Sea test of ten bombs and fourteen bombs in a row, the algorithm fits the multi-target three-dimensional track parallel to each other and distributes it uniformly, which can intuitively and qualitatively judge the correctness of the matching target. In addition, from a quantitative point of view, the test found that the algorithm can not only eliminate the mismatch point, but also suppress the point with large error, thereby reducing the multi-track fit error and improving the multi-target reporting accuracy: the maximum fit error of the track < 0.5m, and the average fit error <0.3m. In summary, this paper proposes a multi-target prediction target reporting algorithm based on three-dimensional trajectory direction estimation, which avoids the detection of image shell explosion points, based on the image shell aerial track detection, conducts three-dimensional trajectory estimation of each shell target, predicts the three-dimensional position of each shell target explosion point, outputs high-precision target reporting information of each shell target, the target accuracy is better than 1m@1km, and supports a multi-bomb continuous target reporting, which can provide scientific and effective data support for training evaluation.

SAR ADC has the characteristics of simple structure, low power consumption, high energy efficiency and good process compatibility. Nowadays, more and more scenarios have higher requirements for the accuracy of SAR ADC. A 14bits SAR ADC with calibration function was designed based on a 0.18μm CMOS process. Design a DAC with a segmented non-binary redundant architecture. Segmented DACs effectively reduce area overhead, while non-binary weighting reduces the effect of capacitor mismatched accuracy, thereby improving ADC accuracy. The simulation condition is that the sampling rate is 1MSPS, and the simulation results show that: Using this calibrated SAR structure, the ENOB is 13.34bits, the SNR is 74.03dB, the SFDR is 81.36dB, and the THD is -79.20dB.

Infrared detecting and tracking system plays an important role in national security. In order to leave enough time to intercept the unknown flying objects, the system needs to” observe” and” report” the objects as early as possible. Due to the long distance and complex background, it is hard to find and locate the small and dim targets. To tackle this difficult task, we propose a hybrid feature extraction network, taking advantages of both convolution and self-attention mechanism. Besides, we use the two-dimension Gaussian distribution to represent the bounding-box, which is convenient to measure the distance between the predicted result and the ground truth comparing to the Intersection over Union measurements. Finally, we also apply multiple data augmentation and training techniques to upgrade the detection performance. To verify effectiveness and efficiency of our method for infrared small target detection, we conduct extensive experiments on a public infrared small target dataset. The experimental results show that the model trained by our method has a significant improvement in detection accuracy and speed compared with other data-based target detection algorithms, with the average precision reaching more than 92%. The proposed method can effectively detect infrared dim-small targets in different complex backgrounds with low false alarm rate and missing alarm rate. It can also achieve outstanding performance in general small object datasets, verifying the effectiveness and robustness of our method.

In this letter, we introduce a very long wave infrared Quantum Cascade Detector (QCD) with a peak response wavelength of 14.5 μm based on a twin-well coupled absorption region design. Different to standard, single transition well QCDs, the twin-well design effectively enhances the absorption strength of the device and broadens the response spectrum to a certain extent. At 77 K, we observed a responsivity of 3.51 mA / W and a Johnson noise limited detectivity of 1×108 Jones. Altogether, this design resulted in detection at temperatures of up to 140 K with a calibrated black-body source by light coupling using a 45° wedge. These high performance very long wave QCDs are expected to provide pollution monitoring, deep space exploration and other applications.

Long-wavelength infrared InAs/GaSb type-II superlattice PπBN photodetectors are demonstrated on GaSb substrates. The focal plane array device consists of a 2.0μm thick absorber layer and has a 50% cutoff wavelength of 11.3μm, and a maximum resistance-area product of 800 Ω•cm2 at 77 K. And the resistance-area product stay above 500 Ω•cm2 at the range from -200 mV to -1100 mV. These single units show good consistency. It has laid a reliable foundation for the manufacturing of focal plane arrays.

The infrared spectra of the Sun include numerous absorption lines, among which He I 10830 Å is one of the most representative spectral lines in the near-infrared band formed in the high-temperature region of the upper chromosphere. The observation of the spectral lines is important for the solar physics research. In this paper, the monochromatic images of sunspots in the He I 10830 Å spectral line was obtained by the one-meter new vacuum solar telescope at the Fuxian Lake solar observation base. The infrared detector using the domestic InGaAs 640×512 focal plane array device can reach a low dark current of 62e-/s/pixel and readout noise of 25.4 e- at 78K by Stirling cooler. The laboratory tests and actual astronomical observations were completed. In the case of large detector readout noise and dark current, a method of extracting the observation target by effectively calculating the flat field was proposed. A monochromatic image of sunspots with He I 10830 Å is obtained for the first time in China using the self-developed detector.

This paper describes the significance of infrared astronomy and the development of infrared detectors for astronomical telescope applications. First, the requirements of astronomical observations on infrared focal plane detector indicators such as dark current, readout noise, and image element size are analyzed, and the infrared detector performance parameters of major domestic and foreign astronomical telescopes in recent decades are summarized. Compared with foreign countries, the performance of domestic infrared astronomical telescopes, especially dedicated astronomical infrared detectors, is still very backward. For example, the readout noise is two orders of magnitude higher than the Webb telescope's 5.9e-, and the dark current is four orders of magnitude higher than the Webb telescope's 0.001e− / pixel∙s. Based on the NIR spectroscopic observation requirements of the 1-meter infrared solar telescope at Yunnan Observatory, we developed a low dark current and low noise 640×512 InGaAs NIR focal plane detector module and a dedicated imaging circuit for sunspot imaging and spectroscopic testing. Measurements using the photon curve transfer method showed that the dark current of the InGaAs NIR focal plane camera was as low as 64e⁻/ pixel∙s, and the average readout noise of the image elements was 25.4e⁻.Finally, the research direction of special infrared detectors for astronomical observation is discussed, and this paper has implications for the research of next-generation astronomical infrared telescopes in China.

Silicon (Si) based photodetectors have been widely used in numerous applications due to their low-cost, high efficiency and good process compatibility. In this paper, a photodetector based on Si mesa heterojunction is reported. Si was doped by ion implantation and used to fabricate a photodetector. The conditions of ion implantation were simulated using a software to obtain the required process parameters before the commencement of the implantation process. The process involved deposition of 100 nm SiO2 film on to the Si substrate, and B ions were injected with 160 keV energy, 6×1014 cm-2 injection dose and at 7° dip angle. After ion implantation, the material was annealed at 900 ℃ for 30 min to repair crystal damages and activate the impurity level. Subsequently, a Si-based mesa heterojunction photodetector was fabricated using a series of standard processes. The photosensitive area of each device unit was 2.04 × 10-2 mm2 . The responsivity of the photodetector in the near ultraviolet and visible bands was more than 0.14 A/W under the bias of -2V. The responsivity of the device was measured using a 1073 K blackbody source, and the voltage responsivity of the blackbody was 1.35×102 V/W. Results from the C-V measurements revealed that the Si has a carrier concentration in the order of 1019 cm-3, which is in good agreement with the simulated results. The experimental results showed that ion implantation has an important effect on the electronic properties of the material and can greatly improve the photoelectric properties of devices.

Photodetectors convert optical signals into electrical signals and have found many important applications ranging from environmental monitoring to communication systems. At present, most photodetectors are based on either bulk materials or epitaxially grown materials (such as InSb and HgCdTe), which limit its widespread applications due to relatively high fabrication cost. However, photodetector based on organic polymer/colloidal quantum dots (CQDs) can provide a low-cost alternative. In this paper, a broadband photodetector consisting of organic polymer phenyl-c61-butyric acid methyl ester (PCBM) and PbS CQDs was fabricated. Combining the advantages of PbS CQDs and organic polymer PCBM, the device demonstrated good spectral response ranging from the UV to the NIR with a maximum responsivity and detectivity of 0.3 A/W and 6.6 × 1011 Jones, respectively, under illumination of 850 nm incident light. The device can be fabricated on almost any substrate due to the solution-processibility of CQDs. Furthermore, the use of organic polymer substrate can significantly reduce the cost of device and broaden its applications (such as in flexible electronics). This work provides a simple and efficient strategy to fabricate photodetector that exhibits multi-band response at relatively low-cost.

HgCdTe has been shown to be the first semiconductor exhibiting single-carrier multiplication in short-wavelength, medium-wavelength, long-wavelength avalanche photodiodes detectors for cut-off wavelengths from 1.3 µm to 11 µm corresponding to compositions xcd from 0.7 to 0.2, which has the remarkable characteristics of high gain, high bandwidth and almost no excess noise. These results have opened a new horizon in photon starved and high-speed applications, such as active imaging and free space optical communications. In this paper, we report the latest results at SITP of HgCdTe eFAPDs using LPE-grown absorption layers in the SW and MW wavelength bands. The gain of single element short-wavelength HgCdTe APD for 2.57 μm cut-off wavelength is about 100 at 25V reverse bias, and GNDCD is about 1.47×10- 7A/cm2 at gain of 100 at 130K. For MW HgCdTe APDs, increase the P region doping concentration will reduce the overall dark current density and eliminate sudden rise of dark current at large bias and high temperature, and lower Cd composition could be a trade-off way for GNDCD suppression. 50 μm pitch 128×128 array HgCdTe APDs for cut-off wavelengths 4.88 µm corresponding to compositions xcd 0.307 were fabricated, whose GNDCD is less than 1×10-7A/cm2 at 8V reverse bias, gain is over 1000 at 11V reverse bias. A 50 μm pitch 128×128 array HgCdTe APDs with xcd=0.29 was manufactured, whose gain reaches 1570 at 9.8V reverse bias, the average excess noise factor is 1.25 at average gain of 133, noise equivalent photon is about 12 at average gain of 113. By thinning the absorption region thickness, the response bandwidth of Hg0.79Cd0.31Te APD reaches 635MHz under 1V reverse bias. Moreover, the medium-wavelength focal plane of 320×256 array is demonstrated the imaging, and the low noise, high sensitivity and fast imaging characteristics of HgCdTe APDs under linear avalanche gain are verified.

In this paper, we report the mid-wavelength HgCdTe HOT (High Operating Temperature) detector with 640×512 array and center distance of 15μm by JueXin Microelectronics Co., Ltd. The detector can work steadily when the focal plane array temperature is 140K. We grew up the CdZnTe substrates by vertical Bridgman technique and HgCdTe materials by liquid phase epitaxy process, then the planar n+-on-p diodes were formed by boron ion implantation. Through the optimization of material growth and device fabrication process, the dark current of the device is reduced. At 140K, the cut-off wavelength of the device is 4.7μm, the dark current density reaches 3×10-7A/cm2, and the dark current density of the device is close to that of P-on-N (rule 07). At the focal plane operating temperature of 140K, the operability of the detector can reach more than 99.5%, the NETD is less than 13mK, and the RFPN is less than 0.6mV (close to temporal noise). At the same low temperature, when the operating temperature of the device changes from 80K to 140K, the power consumption of the detector module is reduced by 37% and the cooling time is shortened by 36%.

HgCdTe electron avalanche photodiodes (e-APDs) with single-carrier multiplication hold great promise for weak signal detection. This work investigates the key metrics that affect the signal-to-noise ratio of mid-wavelength infrared (MWIR) Hg0.7Cd0.3Te e-APD: current, gain, and excess noise factor. The gain is over 1000 at -10 V, but the maximum useful gain is limited by the generation of band-to-band tunneling current at higher bias voltages. The gain dispersion obtained by characterizing the focal plane array is 4.7% at -7 V, indicating a relatively homogeneous gain from pixel to pixel. The excess noise factors evaluated by the noise power spectral density and the gain fluctuation methods both range from 1 to 1.32 at gains below 400, demonstrating the property of near excess-noise-free amplification of HgCdTe e-APDs.

Hollow optical fiber is an important means for transmitting mid-infrared laser radiations (e.g. 10.6 μm CO2 laser) in medical surgery applications. Presently it’s still a challenge to establish a flexible, low-cost hollow fiber that can transmit the invisible mid-infrared light and the visible indicator light simultaneously. In this work, we selected flexible acrylonitrile butadiene styrene (ABS) plastic tubing and polymethylmethacrylate (PMMA) plastic optical fiber to fabricate a PMMA/ABS plastic tube-based hollow optical fiber. The ABS plastic tube with Ag/AgI plating on the inner surface was used to transmit CO2 laser. The PMMA plastic optical fibers integrated around the output end of the ABS tube-based Ag/AgI hollow fiber was used to deliver visible light. The results show that the CO2 laser transmission loss of this hollow fiber goes up from 0.74 to 1.22 dB/m as the bending angle increases from 0° to 120°. The 5-watt CO2 laser can be transmitted continuously for at least 6 minutes. The illumination of visible light transmitted through the PMMA plastic optical fibers can reach 1171 lux. Compared with conventional silica glass tube-based dual- core hollow fiber, the PMMA/ABS plastic tube-based hollow fiber is more robust, flexible and easy to couple. The PMMA/ABS plastic tube-based hollow optical fiber provides new ideas for transmitting invisible mid-infrared light and the visible indicator light simultaneously, which is expected to build a new laser surgery medical equipment.

The laser response of HgCdTe medium-wave photovoltaic device is numerically simulated in this research. The simulations are carried out by considering the carrier electrical properties and a simulation model is obtained, and simulation results are in general conformity with the experimental results under both strong and weak illumination. The saturation threshold increases as the operating temperature of the device decreases, according to the current response characteristics of the device. The contact resistance of device is calculated and discussed, and the optimized device structure are given to point out the direction of parameter optimization. Furthermore, two-dimensional simulations demonstrate that the electrode size and composition gradient and reverse voltage has a considerable impact on the photocurrent, which is an essential problem to address in the development of high saturation threshold mid-wave infrared HgCdTe photovoltaic devices.

The targets on the earth can be detected by its radiation in thermal band from the remote sensing satellite day and night. The State-of-the-art infrared detector technology makes it possible to use thermal focal plane array (FPA) to probe interested target in the boundless sea. Unfortunately due to accidental and uncontrollable factors during detector production, there always are defective detectors in the thermal focal plane array, more or less. We can call it dark element if it has no or weaker response, or can call it hot element if it has abnormal stronger response. These two kinds of defective response cannot be mitigated by linearity correcting, contrarily it will be harmful to the target detecting. Method to identify these defective detectors by analyzing their frequency domain characteristics is stated here. The recognition rate of defective detectors is greater than 98% by using such method.

Recycling scrap metal is an important way to protect the ecological environment. Design effective yet efficient techniques to automatically identify recyclable scrap metals is an important task within this topic. Due to the advantages of fast response and high accuracy, laser-induced breakdown spectroscopy (LIBS) recently played an important role in the mineral identification. However, the identification accuracy of peak-seeking is greatly affected by the data quality of the LIBS spectrum, whereas machine learning methods may be greatly affected by the number of training data. By considering the above open issues, this paper proposes a hybrid algorithm based on support vector machine (SVM) and element peak-seeking. By investing the identified difference of the major element (with the largest composition in the alloy) and the general element (with composition more than 1% in the alloy) between peak-seeking and SVM, three integration types (i.e., rejection, partial acceptance, complete acceptance) are defined. The final recognition result is generated according to different integration types and the corresponding integration methods. To verify the feasibility of the proposed approach, a simulated alloy LIBS database was established based on 31 metal elements and the simulated alloy LIBS data according to their compositions. Comparing with the result obtained by only using SVM, the proposed method greatly improved the recognition accuracy. The accuracy of identifying all general elements increased from 8% to 74.5%. Experimental results confirmed the effectiveness of the proposed method in identification of general metal elements in terms of higher detection accuracy.

Recently, many state-of-the-art methods have been proposed for infrared (IR) dim and small target detection, but the performance of IR small target detection still faces with challenges in complicated environments. In this paper, we propose a novel IR small target detection method named local entropy characterization prior with multi-mode weighted tensor nuclear norm (LEC-MTNN) that combines local entropy characterization prior (LEC) and multi-mode weighted tensor nuclear norm (MTNN). First, we transform the original infrared image sequence into a nonoverlapping spatial-temporal patch-tensor to fully utilize the spatial and temporal information in image sequences. Second, a nonconvex surrogate of tensor rank called MTNN is proposed to approximate background tensor rank, which organically combines the sum of the Laplace function of all the singular values and multi-mode tensor extension of the construct tensor without destroying the inherent structural information in the spatial-temporal tensor. Third, we introduce a new sparse prior map named LEC via an image entropy characterization operator and structure tensor theory, and more effective target prior can be extracted. As a sparse weight, it is beneficial to further preserve the targets and suppress the background components simultaneously. To solve the proposed model, an efficient optimization scheme utilizing the alternating direction multiplier method (ADMM) is designed to retrieve the small targets from IR sequence. Comprehensive experiments on four IR sequences of complex scenes demonstrate that LEC-MTNN has the superior target detectability (TD) and background suppressibility (BS) performance compared with other five state-of-the-art detection methods.

III-V compound semiconductors have abundant features for various electronic, optoelectronic and photonic applications, all arise from variform magic combination of group III and group V elements formed binaries, resulting in ever-changing characteristics. In this paper, diversified ternaries, quaternaries and quinaries are presented geometrically based on the binaries of arsenide, phosphide and antimonide, mainly concerned of their bandgap, lattice constant and the lattice match domain on different substrates. The features of nitride and dilute nitride, bismide and dilute bismuth, as well as boride, are also discussed briefly. An overall observation of whole III-Vs may contribute to the comprehensive understanding of their latent capacity and sustainable development, along with many challenges.

A multi-aperture compound eye infrared optical system is designed for the imaging of cooled medium wave infrared detector. The optical system includes an infrared lenslet array arranged on the front spherical surface, and a relay infrared optical system matched with a cooled infrared detector. The problem of matching and connection between the infrared lenslet array arranged on a spherical surface and the relay infrared optical system matching with a cooled infrared detector is solved, and a set of multi aperture infrared bionic compound eye optical system that can match the cooled infrared detector is designed. Through the relay optical system, the focal surface imaged by the curved infrared lenslet array of compound eye is re-imaged on the focal plane of the cooled infrared detector. The waveband of the designed compound eye infrared optical system is 3.7-4.8μm. The total focal length is 3.5mm, the total field of view of the multi aperture compound eye optical system is 108°, the distortion of the full field of view is less than 6%. The design result shows that the image quality of the system with different aperture approaches the diffraction limit, and has the advantages of multi-aperture, large field-of-view, low distortion and ideal image quality.

Near infrared spectroscopy has been applied to qualitative and quantitative analysis in many fields due to its advantages of fast measurement speed, high accuracy and continuous measurement. Digital micromirror array is an electronic input and output optical mems, semiconductor manufacturing technology combined with the height of the integrated circuit manufacturing technology, make its in resolution, contrast, brightness, grayscale, color fidelity and main performance parameters, such as response time reached the high level, high reliability, fast response speed. In recent years, near-infrared spectroscopy based on wavelength grating and modulation characteristics of DMD has become a research hotspot. This system has the advantages of high signal-to-noise ratio, excellent comprehensive performance and low cost, and has attracted much attention in many application fields. In this paper, the principle, development history, application status and development direction of near infrared spectroscopy based on DMD are reviewed, which provides a basis for the related research of DMD near infrared spectroscopy analysis technology.

Infrared imaging technology has an increasingly wide range of needs in application scenarios such as tracking and detection of high-speed targets and readout of region of interest, and system applications often have requirements for small size and low power consumption. In order to increase the frame rate of the IR detector and solve the difficulty of high power consumption faced at high speed readout, this paper proposes a programmable arbitrary windowing IP module based on a standard digital IC design and achieves ultra-low power optimization of the column-level module of the readout circuit through time-sharing multiplexing techniques. The overall design is a mixture of analogue and digital circuits, with compromises to optimize the area, noise and gain of the circuit, resulting in the integration of analogue and digital circuit layouts. In this paper, a low noise, high speed programmable arbitrary windowing ROIC has been fabricated in the 0.18μm CMOS process, the pixel array is 640×512 and the pixel pitch is 15μm. It is coupled with a short-wave infrared InGaAs detector chip to form a FPA assembly and tested. The results show that the readout rate is greater than 15MHz, the column-level power consumption is only 15mW, the total power consumption is less than 100mW, and the windowing function can be specified in any area with a minimum windowing size of 8×8.

Hg_1-xCd_xTe is considered as the preferred material for high performance infrared photodetectors and imaging focal plane array (FPA) detectors. One of the technical challenges of multi-dimensional integrated HgCdTe epitaxy by molecular beam epitaxy (MBE) lies in the in-situ extraction, characterization and precisely control of a series of parameters such as alloy composition, surface roughness, substrate temperature and film thickness at a relatively low substrate temperature of about 180°C. Therefore, an in-situ, nondestructive spectroscopic ellipsometry (SE) method is needed to characterize the performance of HgCdTe films. In this paper, real time optical property characterization of short-wave Hg_1-xCd_xTe epitaxial grown by MBE is reported. Run to run feasibility and stability of in-situ SE is confirmed by buffer layer thickness verification in multiple growth runs. Lorentz oscillator parametric model provides a new approach to describe optical dispersion property of HgCdTe over spectral range of 1.5-4.1 eV. The absorption peaks show blue shift with the increase of HgCdTe Cd composition (x). Under this circumstance, the longitudinal x value for HgCdTe during epitaxy process can be obtained in real time without any surface damage by successfully building a composition-dependent optical constant library, with routine run-to-run reproducibility measurement accuracy Δx of ~ 0.0015. This work will facilitate the fabrication of HgCdTe heterojunctions with complex component distribution and doping profiles.

SnTe is a new two-dimensional (2D) material, which has many merits, such as the bandgap of SnTe film can be adjusted by changing the film thickness hence its photoelectric properties can be regulated. SnTe belongs to topological crystal insulator (TCI) and has gapless topological surface states as well as exhibiting high carrier mobility at room temperature. SnTe has a narrow band gap and has potential for wavelength extension in the development of novel infrared photodetectors. Si is a traditional semiconductor material and has been widely used in the preparation of various semiconductor devices due to its numerous merits, such as low-cost and well-established preparation methodology. However, the detection wavelength of Si photoelectric detector is limited by its relatively large bandgap (1.12 eV). Recently, some progress has been made in fabricating photovoltaic detectors consisting of new 2D materials and Si. In this study, an efficient and low-cost magnetron sputtering method was used to prepare SnTe nanofilm on Si substrate. A photovoltaic detector based on the vertical heterostructure of SnTe/Si was fabricated using Al as electrode material. J-V characterization of the SnTe/Si heterostructure showed that the device exhibited good diode and photovoltaic characteristics under the illumination of various LED light sources with wavelength between 400 and 1450 nm, and its photocurrent was larger than the dark current. Moreover, under 850 nm illumination, the SnTe/Si device has a high responsivity (R) of 260 mA/W and detectivity (D*) of 3.36×10¹⁰ cmHz^1/2W^-1. Therefore, the device demonstrated potential application in the field of broadband photoelectric detection.

Since infrared detection was proposed, infrared detectors have been to the 3rd generation . Both of the small size and large scale are the requirements for the development of infrared detectors. At present, the focal plane array devices on the market have a relatively high difference between the response wavelength and the size of pixel and therefore, when dealing with long wavelength detection, there will be a large size FPA. The quantum well infrared focal plane array devices fabricated by GaAs/AlGaAs have been widely used due to high uniformity and mature technology, but in the field of long-wave and very-long-wave detection, if the traditional grating coupling structure is used, because the wavelength and the size of the pixel are close, a strong diffraction effect will occur before the infrared radiation reaches the active region. This will lead to significant crosstalk and errors. Therefore, using grating diffraction as the quantum well coupling mechanism limits the size of the pixel and as a coupling mechanism, it is difficult to achieve due to small pixel size. Therefore, this paper adopts the total internal reflection type coupling structure proposed by K.K.Choi, and compare it with the traditional grating coupling structure to study how this structure improves the performance when detecting long-wavelength and reducing the size of pixels. In this paper, a quantum well infrared focal plane array with a pixel size of 640×512, a center-to-center distance of 15 μm and a response wavelength of 10.55 μm is fabricated by using GaAs/AlGaAs and melting photoresist technology which is different with the method proposed by K.K.Choi to fabricate this structure. The FDTD-based open source field simulation software MEEP is used to simulate the field distribution of the devices and evaluate its performance about fighting against optical crosstalk of this structure and compare its performance with the grating coupling structure. In this paper, we also use MEEP to explore the influence of the reflection angle, the position of the active region, and the period of the quantum well on the distribution of the field inside the device, and calculate the electromagnetic wave’s energy of the active region as the evaluation factor. These results shows that these geometrical factors restrict each other, therefore, to produce a good QWIP FPA based on the total internal reflective structure, one need to take these factors into account to tune these parameters to maximize the optimized performance. The main content of the research is to fabricate a 640×512 total internal reflection quantum well infrared focal plane array device, and use the MEEP to study the electrical field distribution inside the device with related geometric factors.

HgCdTe avalanche photodiodes (APD) have been demonstrated to be one of the most promising paths for low flux and high speed applications. The bandwidth of HgCdTe e-APD has been theoretically predicted to be independent of the gain, owed to its strongly dominant electron multiplication. However, when the photocurrent is high, a large number of electrons exists in the depletion region, and the electrical field in the depletion region might collapse due to the space charge effect, thus limiting the increase of the gain-bandwidth product. In this work, the structure of the device was optimized by simulation, and the effect of the light injection dose on the electric field and bandwidth of the device was studied. Finally, a mid-wavelength infrared HgCdTe e-APD device whose bandwidth almost doesn't decrease with the increase of gain is fabricated. The response bandwidth of the APD is about 480MHz @ gain=625, corresponding to a gain-bandwidth product of 300GHz.

The preparation of surface passivation layers on InSb is essential in the process of device fabrication. An Al₂O₃ passivation film was deposited on the surface of medium wave InSb film by atomic layer deposition (ALD). A series of variable area photodiode devices with different P/A ratios were fabricated. The performance of the device is characterized at 77K. The effects of ALD Al₂O₃ and anodic oxidation on the leakage current of diode devices were investigated. The surface leakage current of the passivated photodetectors was reduced by an order of magnitude over the anode sulfidation passivated photodetectors. Moreover, the metal-insulator-semiconductor (MIS) device were developed respectively, and the effects of different films as a dielectric layer on the interfacial characteristics were investigated.

In order to adapt to the third generation of infrared focal plane readout circuit design, this paper designs a 640x512-5μm InGaAs short-wave infrared focal plane readout circuit design based on 0.18μm standard technology. Based on the analysis of each module, the design focuses on the pixel unit and the readout mode of the array. Noise reduction and gain amplification are realized by pseudo correlation double sampling technology. Finally, the design of four - channel output simulation circuit. According to the simulation results, the readout rate is 10MHz, the system default working frame frequency is 54Hz, the output swing is 1.7V, and the linearity is more than 99.9%.

InGaAs/InP Focal Plane Array (FPA) photodetector, which responses from 400nm-1700nm, is widely used in many applications, while its quantum efficiency in visible spectrum is commonly lower than Shortwave Infrared (SWIR) spectrum. In order to improve the quantum efficiency in visible spectrum, new methods need to be applied. Based on Mie scattering, sub-wavelength nanostructure arrays have been demonstrated that can be used as anti-reflecting mechanism in visible spectrum. Here we present the design and simulation of the parameters of nanostructure arrays, which aims at suppressing the reflection in visible spectrum, thus the transmittance of visible light from the back-illuminated side gets improved. Simulation results prove that designed nanostructure arrays can decrease the reflectance in visible spectrum, and integrating designed nanostructure arrays on ultra-thin back-illuminated layer can improve the transmittance, which improves the quantum efficiency of photodetector.

This paper illustrates properties of terahertz electromagnetic wave. Terahertz has been applied widely in areas of military, biologic monitoring, aerospace and environment monitoring. This paper presents application and outlook of terahertz in various areas, which is meaningful to the research of terahertz.

We developed a terahertz scattering-type scanning near-field optical microscopy (THz s-SNOW) to perform imaging tests on the acrosome of sperm. Test results show that the morphology of the whole sperm head could be clearly observed, as well as the outline of the sperm acrosome, which has a clear boundary with the nucleus.

The assembly and measurement of quasi-optical feed network has the characteristics of small size, too many components, compact and complex structure. The measurement and assembly process of quasi-optical feed network has the requirements of high accuracy and high reliability. In this paper, focalizing on problems such as great error in the terahertz quasi ellipsoid lens optical feed networks, slow speed and poor reliability in the traditional assembly accuracy. Putting forward a kind of least-squares surface fitting method with parameter constrains, getting the ellipsoidal mirror, long half shaft and other characteristic parameters, the relative error of fitting characteristic parameters is within 0.03%. We adjust the position of the terahertz quasi ellipsoid from lens optical feed networks based on these characteristic parameters. The experimental results show that, by adjusting the proposed surface fitting algorithm, the assembly efficiency of the terahertz quasi-optical feed network is significantly improved compared with the traditional manual adjustment method, and the assembly error of the terahertz quasi-optical network can be effectively reduced. By the end, the high precision assembly of the ellipsoidal mirror of the quasi-optical feed network can be realized.

The freshness of rice reflects the time that has elapsed since it was harvested and the extent of deterioration in the quality of the rice that has occurred during storage. Therefore, it is crucial to detect the freshness of rice samples; here, we undertake that task using terahertz images and a modified VGG network. Terahertz imaging is non-destructive, permits molecular fingerprinting, and is low in energy consumption. Terahertz imaging technology uses terahertz rays to irradiate the sample and obtains a terahertz image of the sample by processing and analyzing the transmission and reflection spectra of the sample. Terahertz imaging technology has been widely used in applications related to material identification, medical diagnoses, quality detection of agricultural products, and safety inspections. In this paper, terahertz images of rice stored for various lengths of time were analyzed using a terahertz imaging system. Due to a large amount of data and inconspicuous features of the terahertz image, the traditional 1D-VGG network is relatively insufficient in computing power. Thus, it is not well suited to the extraction of features from within the images. To resolve this issue, the Inception-ResNet-A asymmetric convolution module in the Inception-ResNet-V2 network has great computing power,which is introduced into the VGG19 network structure. This proposed network is found to increase identification accuracy up to 99.8%. This work indicates that terahertz images combined with the modified 1D-VGG network represent an efficient and practical method for identifying rice freshness; this work thus has great potential for use as a tool for ensuring food quality and safety.

We have made improvements for QCL in the thermal management to produce high output power. Unlike the previous literature, we use epilayer-down mounting and buried heterostructures to achieve high output power by improving the heat dissipation and reducing the thermal resistance. At 20 K, the continuous wave threshold current density is 110 A·cm-2 and the maximum current density is 210 A·cm−2. The maximum output power is about 250 mW at single facet. The central frequency is approximately ∼4 THz, which matches the energy band design. The thermal simulation shows that, compared with the traditional device, the heat removal performance of the optimized device is significantly improved, and the core temperature is reduced by about 20 K. It improves the heat extraction through epilayer-down mounting and buried heterostructures and leads also to significant lateral heat fluxes. The ways can facilitate the heat extraction in all in-plane directions. In conclusion, this method is beneficial to the development of high continuous wave power, especially for thick active region design. The demonstration of buried heterostructure terahertz quantum cascade lasers for epilayer-down mounting can promote the development of high-power terahertz source in continuous wave.

With the rapid development of terahertz (THz) science and technology, THz transmission has attracted widespread attention. Compared with wireless transmission in free space, THz wave can achieve bending, low-loss and stable propagation in the waveguide. Several types of THz waveguides have been reported. Among them, THz hollow waveguide (HWG) possesses the advantages such as simple structure, easy preparation and low cost. Recently, bendable and low-loss plastic THz HWGs has made progress in our group. This paper gives a review of the research progress in the field of the THz HWGs based on plastic tubing materials, including polymer tube waveguide, metal-coated polymer HWG and metal/dielectric polymer HWG. Problems existing in the plastic HWGs, and key points of future research work were discussed with consideration of some issues aroused in practical applications.

The traditional moldy wheat identification and detection method require complex processing steps, which take a long time and have less feature extraction ability, resulting in poor moldy wheat identification and detection. In this paper, a F-C-BLS terahertz spectral image recognition method for moldy wheat is proposed based on broad learning system. The F-C-BLS moldy wheat classification and recognition model is constructed to enhance the image quality and improve the network feature extraction. Experimental results show that the classification accuracy of our F-C-BLS network is 5.11%, 5.27%, 3.89 and 4.06% higher than that of BLS, RF, CNN and RNN, respectively. Therefore, our algorithm can effectively provide a new and effective method for the early identification of wheat mold.

The fingerprint technology of traditional Chinese medicine is a more effective method to ensure the quality stability of traditional Chinese medicine and control the quality of traditional Chinese medicine. As the core of fingerprint technology of traditional Chinese medicine, terahertz time-domain spectroscopy (THz-TDS) is very suitable for the detection of traditional Chinese medicine. In this paper, a free-space transmission terahertz time-domain spectroscopy system developed by us was used to detect the compound banlangen tablets. The absorption spectra and refractive index spectra of the compound banlangen tablets with different thicknesses, manufacturers and batches were studied. The results showed that: the difference in thickness, batch and manufacturer didn’t affect the terahertz characteristic absorption peak position of compound banlangen tablet, and there were two obvious absorption peaks (1.10THz, 1.17THz) in the tablets; the increase of the thickness caused the absorption peak of the tablet to become smaller and even disappear, and the refractive indexes of tablets with different thicknesses were also quite different; The absorption peaks of tablets with different batches were roughly the same, and the refractive indexes were slightly different; The absorption peaks and refractive indexes of tablets from different manufacturers were basically the same. The above work will help to improve the terahertz fingerprint of compound banlangen, and provide detection means and reference for enriching the quality standard of traditional Chinese medicine.

Experiments for coherent, wide-tunable frequency and high intensity terahertz (THz) free-electron laser (FEL) generation is under preparation at the Shanghai Soft X-ray FEL facility. In this paper, the effect of high order dispersion on a beat frequency-based THz FEL is presented. Theoretical and simulated analysis are carried out, and the results show that the third order dispersion will produce a cubic modulation on the phase of the seed laser, resulting in a degradation of the FEL performance. During the modulation processes, the nonlinear frequency chirp in the seed laser can lead to heterogeneous bunching structure in the electron beam, which will broaden the spectral bandwidth and reduce the pulse energy of THz radiation. To preserve the properties of the THz radiation, limitations on the phase errors of the seed laser are given.

To accommodate variable terahertz application situations, a compact, high-sensitivity and room-temperature terahertz detection module is designed and demonstrated. The detection module with a volume of less than 350 cm³ integrates a quasi-optically coupled terahertz detector, complementary-metal-oxide-semiconductor-based (CMOS-based) voltage amplifier circuit and bias circuit. An antenna-coupled AlGaN/GaN high-electron-mobility transistor (HEMT) are designed to detect terahertz waves by using self-mixing mechanism. The electrical signal from the detector chip is amplified by a voltage amplifier circuit. The amplifier circuit’s voltage gain can be adjusted from 100 to 700 to accommodate different requirements. The bias circuit provides bias voltage to the gate of the detector. Ability to detect both continuous and pulsed terahertz waves by the module is demonstrated. Under a coherent continuous terahertz irradiation from 0.73 to 1.13 THz, an average noise-equivalent power (NEP) of 23.6 pW/ √ Hz, a maximum optical responsivity of 1281 V/W (w/o Gain) and a minimum NEP of 15.3 pW/ √ Hz are achieved. Under a 4.3 THz pulsed radiation from quantum cascade laser (QCL), the module has a peak optical responsivity of 26 V/W (with Gain = 700) and a NEP of 567 nW/ √ Hz. The rise time of the output signal is 1.14 μs and the fall time is 0.78 μs when the module is operated at a maximum amplification gain of 700 and 6 kHz modulation frequency. To further enhance the sensitivity of the detection module, the design of the detector and the noise of the circuit need to be considered.

Water, especially liquid water, strongly absorbs terahertz (THz) waves. Generating or detecting THz waves with liquid water has long been thought impossible. Some recent literatures have reported the successful radiation of THz waves from liquid water, which brings new opportunities for the development of THz-related devices based on liquid media. However, the radiation mechanism has not been well elucidated, and the generation efficiency needs to be further improved. We experimentally show that the application of liquid water lines instead of liquid films as THz radiation sources can effectively enhance THz signals. Generally, the generation and detection of THz waves are considered to be "reversible" physical processes. In view of this, we realized the coherent detection of THz waves for the first time based on plasma in liquid water, filling the gap in the field of coherent detection of THz waves in liquid media. Meanwhile, the THz Kerr effect technique for THz-driven liquid water, as a novel tool, is expected to help explore the low-frequency molecular dynamics associated with hydrogen bonding in liquid water.

Photo-conductive terahertz source (PCA) has been widely used in the terahertz time-domain spectral system (THz-TDS). In the THz-TDS system, the biased PCA is triggered by a femtosecond laser to radiate terahertz waves to free space due to the accelerated motion of photogenerated carriers under the bias electric field, and a pulse current is formed in the PCA bias loop. Generally, the circuit that loads bias voltage to PCA has different circuit designs, so there is inevitably a specific inductance in the base circuit of PCA mounting. The electromagnetic inertia caused by this will significantly affect the pulse width of the current in the circuit. The pulse width of the current pulse will be widened with the increase of the circuit inductance. Therefore, whether the inductance of The PCA circuit will affect the character of the THz wave radiated from PCA to free space is a problem faced by the circuit design based on PCA. In this paper, inductance elements with different inductance values are added to the PCA circuit, and the time domain waveform and spectrum of THz wave radiated by PCA are tested experimentally. The results show that the inductance value in the PCA circuit has no noticeable effect on the THz wave released by PCA, thus providing an experimental basis for designing the THz PCA substrate circuit applied on different occasions.

This paper introduces a measurement system and method of millimeter-wave active pulse radar pattern, which is suitable for the pattern test of small-sized active pulse radar. The measurement system is installed in a small-sized wave-absorbing black box, including positioner, spectrum analyzer, power meter, network analyzer and oscilloscope. LabVIEW virtual instrument programming control technology is used to develop an active pulse radar antenna testing system. Through programming design, millimeter-wave instrument control, the construction and integration of the measurement system are completed, and the actual radar pattern measurement is verified.

Electromagnetic induced transparency (EIT) refers to the phenomenon of a sharp transmission window in a broad absorption profile, which was first discovered in the interference between the electronic transition paths of three energy levels. In this work, a metasurface structure with EIT is designed by coupling a dark-like mode and a bright mode. In order to make its resonance intensity dynamically adjustable, the metasurface structure in this paper adds a structure composed of vanadium dioxide (VO₂) to the original EIT structure. When vanadium dioxide is at different temperature, its conductivity is different, and the degree of participation in metasurface resonance is different. Thus, the dynamic tuning of the EIT resonance intensity is realized, and the modulation depth can reach 76.18%.

The MW gyrotrons are key devices in ECRH of magnetic confinement nuclear fusion systems. In order to achieve the high power and long pulse of the 170GHz gyrotron, which are adopted in the CFETR, a TE2_5.10-mode 170GHz gyrotron research are given in this paper. A single-anode magnetron injection gun (MIG) and the cylindrical resonant cavity operating are designed and optimized by PIC. The theoretical output power of the gyrotron with operating Voltage 75kV, electron current 45A is about 1.1MW, corresponding to electron efficiency of 32.6%. The gyrotron has been fabricated with the single-depressed collector and quasi-optical mode converter and will be tested in the future.

Fengyun-4A (FY-4A) is the second-generation geostationary orbit meteorological satellite series with higher observation frequency and resolution compared with the first-generation in China. While, the spatial resolution (4km) of the infrared channel and water vapor channel is lower than that of the visible light channel (1km), which limits the application of FY- 4A in extreme weather monitoring. At the same time, in order to adapt to the characteristics of the rapid time change of small and medium-scale meteorological disasters, this study based on the deep learning method to downscale the FY-4A satellite data in space and time. The approach consists of two main steps: first, FY-4A data is downscaled using a ESRGAN model transfer learning, which can extract spatially relevant information and reconstruct image resolutions such as infrared channels from 4km to 1km; second, based on the Super SloMo model, the time-related information can be extracted to effectively downscale the FY-4A data, and the temporal resolution of the FY-4A is reconstructed from 15min to 6min , making it comparable to the time resolution of weather radar. The spatial resolution evaluation based on the visible light channel shows that the method used in this study is superior to the spatial downscaling method of bicubic interpolation and Papoulis-Gerchberg in Peak Signal to Noise Ratio (PSNR), Structural Similarity (SSIM), Root Mean Square Error (RMSE), and Correlation Coefficient (CC), and can more effectively convert low-resolution FY-4A satellite data to the corresponding high-resolution satellite data. At the same time, the time-related information can be extracted based on the time downscaling model, the time resolution is converted from 15min to 6min, and the movement direction of the cloud remains the same. Compared with traditional methods, this downscaling approach is a postprocessing method of satellite data with higher precision, which can improve the application value of FY-4A in disaster weather warning.

In the Taiji mission, since the transmission distance of the inter-satellite laser link reaches three million kilometers, the wavefront of its laser transmission will be distorted. Therefore, laser interferometric relative distance measurements can be significantly affected by laser-pointing jitter noise. We built a ground verification system based on the Michelson interferometer to verify critical technologies. At the same time, we analyzed the control characteristics of the system from the perspectives of frequency and time domains. In the end, we successfully built the system in the atmospheric environment of the laboratory and carried out related technical verifications. The experimental results show that in the case of 4µrad/√ Hz@10mHz disturbance, the system can suppress the laser pointing jitter noise to 31.2nrad/√ Hz@10mHz (inner ring data) and 385.7nrad/√ Hz@10mHz (outer ring data), and the effect has reached below the noise floor. The experiment promotes the development of pointing system technology based on the Michelson interferometer and provides relevant technical verification for the follow-up Taiji mission.

Benefitting from advances in photogrammetry and computer vision, 3D point clouds generated from dense image matching have been proved to be an accurate, reliable, and cost-effective data source for lunar topographic mapping. To achieve a full coverage mapping of the lunar surface, a merging of point clouds generated from multiple observations is mandatory. Due to the limit of dense matching accuracy and accumulative registration errors, integrated point clouds normally suffer from disturbed stratification, outliers, and redundant points, resulting in sharp edges between the seams of the fused point clouds. To address the seaming problems of merged point clouds and achieve a seamless fusion result, a weighted fusion strategy evaluating the reliability of points from triangulation errors in the photogrammetry process is proposed. The global registration and post-processing of point clouds are also addressed to optimize the result. With comparisons to other software outputs, a DEM with a resolution of 6 m/pixel is produced, with a lower bias to ground truth and better visualization. As a result, the proposed method can improve the completeness and precision of digital surface model to a certain extent and satisfy the application requirements.

In Fourier Transform Infrared spectroscopy (FTIR), the original interferometric image needs to be pre-processed by apodization, trend term removal and phase correction before the gas irradiance signal can be obtained by Fourier transform, of which trend term removal is the most important. The common method is least squares (LS), which requires high initial values and is susceptible to noise interference. In this paper, M-estimated sample consistency (MSAC) and Genetic Algorithm (GA) are used to remove the trend term from methane FTIR simulated interference data and compare them with the least squares method. The results show that: compared with the least squares method, the MSAC algorithm can improve the trend term fit by about 20%, but the trend term pattern needs to be known in advance; compared with the MSAC algorithm, the GA algorithm has a slightly lower fit effect of about 5%, but requires lower initial values, is more robust and is suitable for situations where the trend term pattern is unknown; combining the two, the GA-MSAC algorithm proposed in this paper, which both reduces the initial value requirement and greatly improves the accuracy of the trend term removal, is of great importance to Fourier transform infrared spectroscopy.

Methane is the second largest greenhouse gas after carbon dioxide, and the measurement and monitoring of methane is essential for regional and city-scale emission reduction strategies. Atmospheric methane concentration observations are also important for predicting regional emission trends. Spectrometers are important optical instruments for monitoring the content of greenhouse gases in the atmosphere, and most spectrometers choose a grating as the spectroscopic element. Due to the higher resolution of the immersion grating, it reduces its volume while improving the performance of the spectrometer and reducing the weight of the whole machine, so it is of great significance to study the immersion grating for the practical application of the spectrometer. In this paper, the quartz immersed grating was designed for weak CH4 band. The rectangular groove structure with high refractive index dielectric film was designed in consideration of possible fabrication errors. In the 2.275-2.325μm band, the duty cycle of the rectangular groove is 0.3~0.45, the thickness of TiO2 is 165~170nm and the groove depth is in the 800~980nm region, the diffraction efficiency of the grating is higher than 70%. When the thickness of TiO2 is 170nm and the groove depth is in the 800~950 nm region, the diffraction efficiency of the grating is higher than 80%. When the TiO2 thickness is 175~180 nm, the overall polarization degree is less than 0.1. For trapezoidal grooves, when the duty cycle is 0.3~0.35, the bottom angle of the trapezoid is 80°~86°, the thickness of TiO2 is 195 nm, the depth of the grating groove is 820~900nm, and the diffraction efficiency can be above 80%. When the thickness of TiO2 is 177~195nm, the polarization degree is less than 0.1. The TiO2 film will be deposited by atomic layer deposition.

With the increasing frequency of space activities, space satellite systems are fully involved in joint operations. Numerous imaging and reconnaissance optical imaging satellite systems are arduous to evade and warn actively, and passive protection is cumbersome to implement. Therefore, developing new reflective imaging satellite reconnaissance systems and materials is particularly important. In countering optical imaging satellites, active jamming materials can form aerosol jamming smoke screens on the action path of the target to be protected. The jamming signal transmitted in all directions can suppress the imaging accuracy of the optical satellite to the target and form an effective deception. CsPbBr₃ perovskite quantum dots show great potential in anti-detection and active jamming due to their high absorption and emission efficiency, size-dependent excellent photoelectric properties, and low exciton binding energy. However, it is still challenging to synthesize CsPbBr₃ nanosheets with wide band emission for active interference. This paper uses the template induction method to regulate the morphology of the CsPbBr₃ crystal. CsPbBr₃ nanospheres and nanocubes were synthesized by the recrystallization method. CsPbBr₃ nanospheres were induced to self-assemble on CsPbBr₃ nanocubes to synthesize CsPbBr₃ nanosheets with wideband emissions. It maintained a strong quantum confinement effect, a simple synthesis process, high stability, and excellent photoelectric performance. The induced synthesis process was recorded by field emission transmission electron microscope. The nanosheets were face-to-face, close, and perpendicular to the carbon film substrate. The balance of van der Waals force and elastic repulsion force between ligands under thermodynamics determines the lamellar spacing of nanosheets in the self-assembled state. UV-Vi's absorption spectra further proved the change of morphology during self-assembly. The nanosheets were also very stable under 200kV electron beam bombardment. The fast Fourier transform patterns of the nanosheet demonstrated that the assembled NCs were orthogonal, with no crystal transition in the assembly process. X-ray photoelectron spectroscopy showed that the crystal is composed of CS, Pb, and Br elements. The assembly process did not change the ion state and element composition on the surface and inside. The photoluminescence spectrum showed that the emission wavelength of the nanosheets was 493nm, and a uniformly tunable emission wavelength was generated between 468-506nm. The disappearance of the tail band in the long wavelength region demonstrated that the defects in the self-assembly process were significantly reduced. The quantum yield increased from 65.78% to 67.33%, which directly confirmed that the large absorption cross section and defect reduction brought by the unique sheet structure were conducive to the conversion of excitation light in the active interference process. This paper provides an idea for the theoretical study of morphology regulation of perovskite nanocrystals and other system nanocrystals. Most importantly, the high coincidence between the steady-state fluorescence spectrum and the response curve of the Si-based CCD attested that quantum dots could be used to interfere with the optical imaging system based on CCD actively.

We present a general half-quadratic based hyperspectral unmixing (HU) framework to solve the robust or sparse unmixing problem. A series of potential methods can be designed and developed to solve HU problem through this framework. By introducing correntropy metric, a correntropy based spatial-spectral robust sparsity regularized (CSsRS-NMF) unmixing method is derived through the proposed framework to achieve two-dimensional robustness and adaptive weighted sparsity constraint for abundances simultaneously.

The OSIRIS-Rex Laser Altimeter (OLA) is the first scanning lidar instrument to fly a planetary mission. The OLA scans Bennu for about a month during the Orbit B mission phase and obtains 911 frames of point clouds. Due to the uncertainty of spacecraft position and pointing, there will be offsets between overlapping point clouds. In our method, the point cloud is first projected onto a plane, and then the keypoints are extracted using the SIFT algorithm. Finally, we perform coarse and global adjustments based on keypoints. However, low accuracy of the corresponding keypoints will lead to bad registration. In order to improve the accuracy of keypoints matching and point cloud registration, we use the tuple test and RANSAC algorithm to eliminate mismatched points. For the overlapping point clouds of two frames, the RMSE between keypoints is about 0.04m after registration. The results show that this method can improve the accuracy of point cloud registration to a certain extent and meet the application requirements.

The performance of the Advanced Geosynchronous Radiation Imager (AGRI) onboard the Fengyun-4 (FY-4) satellite was evaluated. The results showed that its performance has approached the international advanced level of similar instruments. A wavelet filter was designed to filter the striping noises of the AGRI, which come from the inconsistency of the spectrum and thus varies with the observed target. The non-uniformity of the whole image was evaluated by weighting the probability variance of its count values. After filtering, the infrared image of the AGRI had a uniform visual effect on a single channel, and the pattern noise was reduced to below 0.2 K, which ensures the uniformity of products such as cloud detection and sea temperature that use the infrared splitting window channels. Furthermore, the AGRI carries the surface source blackbody as the on-orbit radiation calibration benchmark and rotates the north-south scanning mirror to point to the blackbody to obtain the blackbody observation data in each infrared band. In the current mode, the infrared calibration is performed every 15 minutes. The long-term evaluation results showed that the radiation calibration accuracy of the infrared channels of the AGRI was better than 0.5 K, and some of the channels reached 0.2 K. In addition, the long-term monitoring of the sensitivity and radiative cooling of the AGRI has shown the on-orbit variation of the instrument, which provides a reference for the development of the subsequent instrument.

The successive launches of hyperspectral satellites have provided a rich data source for soil quality monitoring. Soil Organic Matter (SOM) is an essential soil quality indicator. How to use multi-source hyperspectral data for cooperative monitoring to obtain SOM content is an important issue in black soil surveys. In this paper, a spectral index of SOM applicable to collaborative monitoring with multi-source hyperspectral data is developed for the black soil region. First, a series of spectral indices were constructed by combining spectral transformations (such as reciprocal and square root) and dual-band index formulas (such as ratio and difference), respectively. Then, the Pearson’s correlation coefficient (ρ) of SOM and all the spectral indices were calculated for each dataset. Finally, the optimal spectral index of SOM was determined based on the ρ of different datasets. The results show that the optimal spectral index of SOM is DIOR (560,600). The R2 of the exponential fit reaches 0.54, indicating that DIOR (560,600) can effectively characterize the soil organic matter content. Also, DIOR (560,600) is stable and simple to calculate, showing great potential in SOM estimation of black soil using multi-source satellite hyperspectral data.

Thermal infrared remote sensing plays an important role in the field of optical remote sensing because it can obtain the radiant brightness temperature of ground objects day and night and provide basic data for quantitative applications such as surface temperature and evapotranspiration. In order to improve the observation efficiency of long-wave infrared remote sensing, after years of pre-research and model engineering development and test verification, a 360° unidirectional uniform rotation scanning mirror is set in front of the optical lens, a small F-number optical lens is configured, and a high-sensitivity quadrangular integrated long-line TDI long-wave detector is set. The on-orbit application of a wide thermal infrared imager with a spatial resolution of 100m, NEΔT better than 0.1K and width better than 1500km in four long wave infrared spectrum segments of 8μm～12.5 μm has been realized, which makes the comprehensive index of thermal infrared optical load in China reach the international advanced level. The stability of the high and low temperature blackbody of the large surface source can reach 20mK/25min, and the temperature difference can reach 21℃, which provides a guarantee for the high-precision radiometric calibration and quantitative application in orbit. The payload can cover most of the regions in China in one day and the whole world in two days, which will greatly improve the application efficiency of thermal infrared remote sensing data, and provide powerful data support for thermal pollution emission monitoring, environmental assessment of nuclear power plants, water temperature monitoring of key rivers and lakes/coastal areas, drought monitoring, fire monitoring, etc.

UV detection technology has great advantages for the effective detection of space targets. Due to the immediacy of the space detection target, it is difficult for the detection system to capture the target. When detecting the space target, it is necessary to select appropriate bands and set effective instrument parameters to increase the capture probability of the space target. At the same time, the field experiment process of space target detection by detector is relatively complex and difficult, so it is difficult to obtain such data. In the absence of test data, in order to make the UV detection system can set effective detection band, and ensure the good test and quickly obtain the radiation characteristics of the longrange target, simulation method is used in this paper. In an experimental way, in the case of unknown atmospheric conditions and composition, a model for calculating the near-surface long-range target radiance in UV band is constructed, which simplifies the radiative transmission process of the signal in the atmosphere. In this paper, the radiation of target in UV band is studied, and the mathematical model of radiation calculation is established. The research results have certain engineering application value. In the field test, it is difficult to determine the atmospheric transmittance between the camera and the target due to the lack of estimation of the atmospheric composition at the launch time, which makes it difficult to accurately estimate the radiation of the long-range target at near-surface in the test site. To solve this problem, the ultraviolet (UV) band was divided into two parts, that were target band (240nm~280nm) and background band (300nm~400nm). By simulation, the estimating models of atmospheric transmissivity were separately established in the two bands. And then the long-distance target radiance was estimated only according to the distance for successive two times between the detector and target in a short time. Compared with the radiance of blackbody simulated, the relative error is about 9.87% in the target band, but only 0.11% in the background band. The research can provide technical support for UV detector to effectively detect the long-range target radiance.

The physiographic map can visualize spatial relations between different landforms, thus providing insights into geologic processes that shaped the present-day Martian landscape. The physiographic map of Mars surface is usually made through image interpretation, which is always labor-intensive and highly depends on the expert knowledge. In this paper, we propose an efficient and automatic classification method for characterization of landforms on Mars by using the Mars Orbiter Laser Altimeter (MOLA) digital elevation data. The proposed method was tested on a region where China's Mars probe Tianwen-1 landed. The study area covers the Nepenthes Mensae, Amenthes Planum, northern Terra Cimmeria, northern Hesperia Planum and southern Utopia Planitia region, having a size of 2250km×2750km centered at 117°E, 6°N. The obtained results confirm the effectiveness of the proposed method in describing different topographic characteristics of the Martian landforms. Note that the proposed method is completely data-driven, which can provide a rapid mapping result in large geographical regions, especially from a global perspective to reveal the Martian landform information.

Long-life mechanical refrigeration technology is an important technology which provides support for space scientific researches and exploration. The cryocooler can reduce the background noise and improve the signal-to-noise ratio, sensitivity, and resolution of the optical detector. The cryocoolers play an important role in infrared detection that provide an essential low temperature working environment for infrared detectors and equipment. Nowadays, the sensitivity requirements of infrared detectors have increased, and it is gradually necessary to provide a cooling temperature region below 20 K. It is also necessary to provide cooling in the liquid helium temperature region for the very long waves and microwaves infrared detection. Stirling type pulse tube cryocooler (SPTC) has become one of the most popular mechanical refrigerators due to its advantages of no moving parts at the cold end, low vibration, high stability, and simple structure. In the form of multi-stage coupling, the SPTC can realize the space application in the temperature range of 4-20 K, and a series of multi-stage cryocoolers have been developed in Shanghai Institution of Technical Physics of Chinese Academy of Sciences (SITP, CAS). A two-stage SPTC operating in 20 K (PT2C-20) has been developed for cooling infrared detectors and per-cooling helium JT cryocooler. For easy adjustment and high efficiency, the driven compressor of the SPTC is designed as two independent linear compressors. The second stage cold finger uses an active warm displacer as phase shifter to maximize the cooling performance. By optimizing the operating parameters of the active warm displacer piston and the pre-cooling temperature, the cryocooler can obtain a maximum cooling capacity of 1.31 W at 20 K with the total input electrical power of 470 W and the pre-cooling temperature of 80 K. For the multi-stage pulse tube cryocoolers working at 20 K, the design of the regenerator in the low temperature section is the key to improving the cooling capacity and efficiency of the refrigerator. In order to further lower the no-load temperature and improve the efficiency of the cryocooler at 15 K, we studied the influence of the regenerator in the low temperature section of the second stage pulse tube refrigerator by simulation and experiments. The structural parameters of the regenerator and other key components were optimized and improved, and a new two-stage SPTC (PT2C-15) was designed for the 15 K temperature region. The cryocooler can obtain a cooling capacity of 0.91 W at 15 K with a total input electrical power of 386 W whose cooling capacity and efficiency are greatly improved. In order to realize the applications of liquid helium temperature region, we have developed the three-stage pulse tube cryocooler technology, especially for the large cooling capacities. A third-stage SPTC is thermally coupled with the developed two-stage SPTC (PT2C-20) and successfully obtained a three-stage SPTC (PT3C-7) which can work at 4-10 K. Within the total input electrical power of 500W, the PT3C-7 with He-4 as working fluid can obtain a minimum temperature of 3.96 K, and a typical cooling capacity of 145mW at 7 K. The development in the multi-stage SPTC working in the temperature range of 7-20K of SITP, CAS will provide very low-temperature technical support for detection in the field of infrared astronomy.

As a main element of China second generation of geostationary meteorological satellite Fengyun 4B (FY-4B), which was launched on Jun. 03, 2021, the Geostationary High-speed Imager (GHI) is the first round the clock high-frequency imaging instrument working on the international geo-stationary orbit. It can continuously observant and imagine for 2000km×2000km regions with spatial resolution up to 250m in 1 minute interval. The challenge of GHI thermal design was that the sun intrusion of the optic system would induce destabilization of the internal temperature field. It conflicted with the target of the GHI thermal system, which should ensure small temperature difference between two sides of scanner shrouds (less than 3K), the low temperature gradient of optical mounting platform (less than 2K), and high precision temperature control (±0.1K) of blackbody. This paper described the control strategy and requirements of the GHI thermal system, which successfully performs all phases of the mission. The on-orbit data showed that the instrument maintained a stable internal thermal environment when optical system exposed to external heat flux disturbances in mid-night.

Since Hyperspectral images (HSIs) contain a large amount of spectral information, they can provide detailed spectral information and enable accurate CD. However, the spectral heterogeneity of HSIs may lead to false alarms which will reduce detection accuracy. Additionally, it is difficult to collect and annotate pixel-level labels for CD in HSIs. Therefore, we propose an unsupervised symmetric tensor network (USTN) for HSIs CD. We design a novel multidimensional symmetric tensor framework to solve the problem of high-dimensional data processing. Furthermore, the framework integrates a spatial edge loss to preserve detailed spectral-spatial information. Finally, we use feature fusion to suppress the invariant components (i.e., the background) and highlight the variant components (i.e., temporal changes). Experiments on two sets of multitemporal HSIs, Hermiston and Bay Area, demonstrate the effectiveness of USTN for binary change detection.

Deep space exploration is an important way for mankind to innovate space science and technology, and to promote the development and utilization of space resources. Remote sensing technology plays an extremely important role in these exploration missions. Visible and near infrared reflectance spectra are the effective means to study the composition of celestial objects. The Chang’E-5 (CE-5) lunar exploration mission has achieved China’s first sample return from the moon, helping scientific research on the origin and evolution of the moon. The landing areas of CE-5 and Apollo 12 were located in the north and south of the Oceanus Procellarum, respectively. In this paper, the spectral data of the craters near the CE- 5 landing site and the similar Apollo 12 lunar rock (12063) spectrum with its mineral composition are compared and analyzed. The band area ratio method and the modified Gaussian model method were applied to study the spectral characteristics and mineral composition of these craters and rocks. The chemical compositions and evolutionary trends of major constituent minerals are consistent with the basalts returned by the Apollo missions. The spectral deconvolution results indicate that the mafic minerals in the crater rocks near the CE-5 landing site are dominated by clinopyroxene, followed by orthopyroxene and olivine, which is significantly lower than the orthopyroxene mineral abundance in the Apollo 12063 lunar rock. It may indicate that the young basalts of CE-5 landing area originate from the lunar mantle source region, which is rich in clinopyroxene and contains a small amount of olivine material. Remote sensing and space exploration help us solve many meaningful scientific problems. In general, remote sensing is an important and useful, even the only, means for us to understand the solar system and extrasolar celestial bodies.

Sea surface temperature (SST) is a key parameter for monitoring the ocean environment and understanding various ocean phenomena, and is a key indicator of climate change. Satellite remote sensing data is an important technical tool for SST research, but the availability of data is reduced due to the influence of clouds and aerosols, which generate a large amount of missing data. The data interpolation empirical orthogonal function (DINEOF) method has usability and accuracy in reconstructing missing grid points of remote sensing datasets. In this study, we use a convolutional self-encoder neural network, modified for model skip connection and fully connected layers, and introduce an attention mechanism to extract spatio-temporal features of SST data, called attention data interpolation convolutional autoencoder (A-DINCAE), to achieve the reconstruction of infrared radiometer SST data and compare A-DINCAE with DINCAE and DINEOF Reconstruction accuracy. The accuracy of the reconstruction results is quantitatively evaluated using cross-validation datasets and actual measurement data, and the study area is selected as the South China Sea with the boundaries of 103-121°E and 0-23°N. The validation results show that the reconstruction effect of the A-DINCAE model on the SST missing data is better than that of DINCAE, the accuracy of the reconstruction results is much higher than that of DINEOF, and the reconstruction results restore the main SST of the sea area physical features of the sea area. This paper confirms that the attention mechanism can improve the DINCAE spatio-temporal feature extraction ability, and the small-scale features of the missing data are restored under the same data reconstruction conditions, and the A-DINCAE is more efficient than DINEOF, and The accuracy of the improved model has been improved.

Infrared focal plane linear array detector is the core element to achieve high spatial resolution and high radiometric resolution infrared imaging. Due to the difference of detector response rate caused by non-uniform materials and the high sensitivity of camera to background signal changes, the complex non-uniformity of the image is eventually caused. In order to identify targets effectively and quickly, real-time non-uniformity correction must be performed on infrared camera images. The most commonly used method is to obtain the correction coefficients of each pixel based on variable temperature blackbody calibration before each image. However, it is difficult and costly to design full-aperture calibration blackbody for infrared camera with wide field of view and high resolution, and the feasibility is not high. In order to correct the non-uniformity of the acquired image, this paper proposes a non-uniformity correction algorithm for single-scene infrared image based on finite constraints. According to the principle that the pixel response rate is basically unchanged, the algorithm establishes a constraint relationship between the response rate of each probe element obtained by laboratory calibration and the response rate of the central standard pixel to iteratively screen the samples involved in the correction coefficient calculation, so as to realize the non-uniformity correction of the image. The proposed algorithm was verified by using the location imaging data of the medium-wave infrared camera. The non-uniformity of local uniform image was 44.1% before correction, and decreased to 4.4% after correction, while the uniformity of conventional scene correction was 13.5% after correction. Therefore, the non-uniformity of the proposed algorithm is reduced by 9.13% compared with the conventional scene correction method. The algorithm successfully breaks through the design limitations of no star calibration device of the wide-field high-resolution infrared camera, improves the target recognition efficiency of infrared image, and is conducive to implement in engineer. In addition, it only takes about 1min to correct an image of 30000 pixel *30000 lines by testing.

In this paper, the influence of the noise and acquisition device resolution of the system is researched on Homodyne Interferometric Angle Measurement Based on Ellipse Fitting. The research method combining data simulation and experimental verification is adopted. The influence of noise and acquisition resolution on the angular resolution is obtained by comparing the experimental and simulation results. The experimental verification results are consistent with the data simulation results. The system angle measurement resolution reaches 10-5 rad, and the system noise error is between 3%- 8%.

The thermal drainage of coastal power plants have adversely affect the ecological environment in the nearby sea area. Thermal infrared remote sensing data has the characteristics of macroscopic and periodic revisiting, and has certain advantages in monitoring the sea surface temperature and the thermal drainage of coastal power plants.FY-3D MERSI-2 thermal infrared channel data has 250m spatial resolution and once a day revisit cycle, it has potential application value in the sea surface temperature monitoring. In the construction of sea surface temperature retrieval model, it is necessary to deal with all kinds of data needed for the construction of the experiment, including atmospheric profile data set, emissivity data, spectral response information, ocean station data, MODTRAN atmospheric radiation transmission simulation model data, etc., to meet the needs of the experimental process. A high-precision model temperature retrieval model based on split window algorithm is constructed by using FY-3D MERSI-2 thermal infrared channel data. It is used to retrieve the sea surface temperature in the waters near Fuqing nuclear power plant and analyze the environmental application problems such as the diffusion trend, temperature change trend, the form of thermal drainage and the distribution of temperature rise zone. Firstly, the FY-3D MERSI-2 data is subjected to geometric correction with the Geographic Lookup Table (GLT), and radiation correction to obtain the image brightness temperature data. Then, the sea surface temperature is retrieved according to the established model, and it is matched with the thermal infrared data of Infrared Multi-spectral Imager of Gaofen-5 (GF-5 VIMS), with a spatial resolution of 40m in spectrum and geometry. Finally, the retrieval results of the two images on the same day are compared. The retrieval results are verified by the measured data, and compared with the retrieval results of the traditional split window algorithm retrieval models. The results show that: Based on the split window algorithm, the sea surface temperature retrieval model established by adding two thermal infrared channel temperature difference terms is better than 1.7K in accuracy. Because of its high frequency of time revisiting, the MERSI-2 data can monitor the distribution of temperature and drainage in different seasons and tidal levels. According to the statistics of base temperature, temperature rise area, tide and temperature rise diagram of FY-3D MERSI-2, it can realize ideal spatial distribution monitoring of warm water and drainage. According to the form of warm drainage, the monitoring results of GF-5 VIMS are relatively fine. After being discharged through the water outlet of the sewage pipe, due to the influence of the instantaneous sea surface wind direction and wind speed, it will be discharged to the southeast, and its diffuse shape is obvious. For small-scale power plants, it is suggested to combine the thermal infrared remote sensing data with high spatial resolution to improve the monitoring accuracy of time frequency and diffusion details distribution of thermal drainage in power plants. In the future research, if there are conditions to measure or collect more relevant environmental data, such as sea surface wind direction record, sea area circulation record, etc., there will be more beneficial to further analyze the distribution and change of temperature and drainage in the study area.

The life ecology experimental cabinet on China Space Station is a microgravity scientific experimental platform which is suitable for plant individuals, fish, snails, fruit flies and other biological individuals as the research objects. It includes a general biological culture module (GBCM), a small general biological culture module (SGBCM), a small centrifugal experiment module (SCEM), a small controlled life ecological experiment module (SCLEEM) and a microbial online monitoring module (MOMM). The GBCM provides suitable environmental conditions for biological experiments, including temperature, humidity, light, gas concentration, visible light imaging detection, fluorescence imaging detection, program-controlled instructions, etc. The SGBCM internally provides temperature control and imaging monitoring. Other functions are realized by the replaceable culture unit. The SCEM can realize 1-2g gravity simulation in microgravity environment, and is able to support variable gravity biology research and microgravity comparison experimental research. In SCLEEM, it is planned to carry out a closed aquatic organism culture experiment with algae, fishes and snails as members. Algae provides necessary oxygen for fishes and snails through photosynthesis. MOMM is a payload used to detect the presence and classification of microorganisms in the environment. Each module works independently and has an independent electronic control system with the same architecture.This paper will introduce its basic functions, experimental conditions and expandable interface resources module by module. It provides a basis for space biologists to design experiments and a reference for payload engineers.

Infrared target recognition is an important task in space-situational awareness. In the space target detection process, due to the small energy of the point target, it is easy to make the target disappear from the detection field of view under the interference of dense noise, resulting in a decline in recognition system performance. Reasonable representation of the infrared characteristics of a target is an effective means of improving the stability of recognition systems. In this study, a one-dimensional radiation intensity sequence was mapped to a two-dimensional space based on the Gramian angle field, Markov transition field, and recurrence plots to visualize the structural mode of the target radiation intensity sequence and the dynamic properties of the system generating the sequence. On this basis, a recognition framework based on convolutional neural networks was proposed to train and recognize three types of visualized signals and raw data. The experimental results showed that the proposed recognition method based on visualized signals can effectively identify the target and is robust against noise interference and missing data.

The operating principle of the static Martian wind imaging Michelson Interferometer (MWIMI) developed by our research group is discussed in this paper, and the errors caused by the core components of the interferometer are analyzed, including the tilt of the quadrangle fixed mirror, surface heterogeneity and reflectivity errors. This work mainly studies the influence of error on the measurement of wind speed and temperature, and the error curve is obtained by computer simulation. The limit of tilt angle, surface accuracy and reflectivity of the four-quadrant fixed mirror can be obtained from this curve. Ultimately, the accuracy of the MWIMI instrument is discussed according to the actual design parameters, which verifies the high measurement accuracy of the instrument. This study lays a theoretical foundation for the design, development and engineering of a new type of wind imaging interferometer, and provides a reference for the study of Mars atmosphere, which is of great significance for the climate change, environmental detection and space exploration of Mars.

Mechanical cryocooler technology are one of the significant technologies for earth and space scientific exploration. To meet the needs of future applications of infrared and millimeter wave detectors, Shanghai Institute of Technology Physics, Chinese Academy of Sciences (SITP, CAS) has developed a helium Joule-Thomson cryocooler (JTC) below 4.5 K for space applications. As the two most important components of the helium JT cryocooler, the precooler and the JT compressor are both developed by SITP. The precooler is a two-stage pulse tube cryocooler, and the JT compressor is an oil-free linear compressor, all of which can achieve long-life operation. First, a 4 K JTC was developed, experimental results show that after about 11 hours of cooling, the 4 K JTC successfully reached the liquid helium temperature and has a cooling performance of at least 110 mW@4 K.

The two stages gas-coupled Stirling/pulse tube refrigerator (SPR), whose first and second stages respectively involve Stirling and pulse tube refrigeration cycles, is a promising spaceborne refrigerator. The SPR has many advantages because of the unique configuration combining each feature of the Stirling and pulse tube refrigerators, such as compact structure, high reliability, and outstanding performance. A SPR-20 has been designed and manufactured. When all of the regenerators are filled with stainless-steel mesh, the SPR-20 can obtain 2.6 W at 70 K plus 0.1 W at 20 K with 160 W total input power. While the second stage regenerator is mixed filled with magnetic material and stainless-steel mesh, the cooling capacity of the SPR-20 can be improved to 2.5 W@70 K plus 0.45 W@20 K with 200 W electric input power plus 17 W displacer input electrical power. Meanwhile, the SPR can obtain 0.32 W at 15 K plus 0.65 W at 65 K with 250 W compressor input power plus 20 W displacer input electrical power. The performance of the developed Stirling/pulse tube hybrid refrigerator (SPR-20) has a relative advantage among 20 K high-frequency refrigerators.

The imaging spectrometer monitoring the CO₂ content in the atmosphere is mainly divided into the weak CO₂ band and the strong CO₂ band. Compared with the strong CO₂ band, the weak CO₂ band has a relatively clean spectrum, less interference from water vapor and other gases, and weaker CO₂ absorption, and the instrument can receive stronger groundreflected solar radiation signals. However, the concentration of CO₂ in the atmosphere is low. To use this band to detect changes in CO₂ concentration, it is necessary to ensure that the detection instrument has a sufficiently high spectral resolution. Using the immersion grating as the dispersive element in the spectrometer can greatly reduce the size and weight of the instrument while achieving high spectral resolution. In this paper, the quartz immersion grating used in the weak CO₂ detector is optimized and designed, the groove parameters of the grating are designed and optimized according to the requirements of the weak CO₂ detector used, and the rectangle and different bottom angles are designed and optimized in consideration of the actual production error. In the 1.595-1.625 μm band, the duty cycle of the rectangular groove is 0.3-0.35, the groove depth is 560-630 nm, and the TiO₂ thickness is 110-120 nm, the diffraction efficiency of the grating is higher than 80%; the duty ratio is 0.4-0.45, When the groove depth is 590-660 nm and the TiO₂ thickness is 100-105 nm, the diffraction efficiency of the grating is higher than 80%. When the duty ratio of the trapezoidal groove is 0.3-0.35, the bottom angle of the trapezoid is 82°-86°, the groove depth is 590-630 nm, and the TiO₂ thickness is 120-125 nm, the diffraction efficiency of the grating is higher than 80%. When the duty ratio of the trapezoidal groove is 0.4-0.45, the bottom angle of the trapezoid is 82°-86°, the groove depth is 620-670 nm, and the thickness of TiO₂ is 105 nm, the diffraction efficiency of the grating is higher than 80%.

The processing of bathymetric data of multi-beam echo sounders is required in the hydrographic and oceanographic field. The algorithm CUBE allows automatic processing of data to estimate the depth of the sea floor through multi-beam data. To implement the CUBE algorithm, it is important to set the parameters in the data processing. Depending on the complexity of the survey, the optimization CUBE setting is essential to ensure the quality of results of data processing. In this paper, the optimization of CUBE algorithm, which is based on the configuration of the algorithm parameterization, is used to optimize the parameters of CUBE algorithm to improve the quality of data processing on shallow water for multi-beam echo-sounder. First, the behavior of CUBE is described through some different parameters to a new parameterization more suited to the EM2040C sounders. Then, tests of the CUBE parameterization are carried out with the aim of obtaining an optimal parameter configuration. Finally, the influence of parameters is analyzed by statistics methods to explain the feasibility of using CUBE algorithm to parameterize data processing on shallow water. Experimental results with the shallow water dataset demonstrate the majorization and effectiveness of the CUBE parameters setting for situations of the survey in areas of small depths.

Hyperspectral unmixing aims to correctly estimate the endmembers and their corresponding abundance fractions in an HSI. Many hyperspectral unmixing methods have been proposed, including the longstanding geometry-based, statistics-based and non-negative matrix factorization (NMF)-based unmixing methods. The traditional NMF-based method expands the three-dimensional hyperspectral data into matrix form and decomposes it into the product of the endmember and the abundance, which causes a certain degree of information loss. The matrix-vector nonnegative tensor factorization algorithm solves this problem well by processing hyper-spectral data as a tensor and pioneers a new model based on tensor decomposition. However, such methods still suffer from underutilization of image information and unstable performance at low signal-to-noise ratios (SNR). To solve this problem, we proposed a new superpixel-based spatial weighted sparse nonnegative tensor factorization unmixing model (SupSWNTF), which better exploits the spatial information and improve the sparsity of the solution by adding constraints to the abundance matrix. A series of comparative experimental results on synthetic and real-world data sets show that our algorithm achieves the best unmixing results compared to other state-of-the-art algorithms.

The infrared (IR) benchmark sounder is designed to detect the tiny change of long-term global climate by measuring the spectrally resolved IR radiance emitted from Earth to space with high accuracy. Besides, the IR sounder also serve as a space-borne radiometric reference to convert the international fleet of weather sounders into a climate benchmarking system with excellent global coverage and similar measurement accuracy. In order to achieve high accuracy, the benchmark sounder must be tuned to be a linear response system and be well radiometrically calibrated. So the nonlinearity response in an IR detector signal chain needs to be corrected prior to the linear radiometric calibration. There are some algorithmic approaches being commonly used to correct the nonlinear measurements. These methods use the measured nonlinear interferograms to polynomially fit the corrected linear interferograms, without considering the physical root of non-linearity. However, they work well only when the detector nonlinearity is small. Regarding the large nonlinearity, a correction method is proposed in this paper. It follows the nonlinearity response mechanism of the IR detector, and uses the to-be-solved linear interferogram to polynomially fit the measured non-linear interferogram signal formally, and then derive the correction coefficients from the established equations. According to the correction evaluation and methods comparison using the simulated data as proxy measurements, the proposed method is appropriate for both small and large degree of quadratic nonlinearity detectors.

Space-based infrared detection, which plays an important role in both national safety and people's daily life, is an essential means of aerial surveillance. However, the traditional performance characterization method used in the current system is difficult to distinguish aerial targets from complex backgrounds effectively, which is mainly manifested as low signal-to-clutter ratio (SCR). In this paper, a novel characterization method based on infrared differential analytic factor (IDAF) is proposed to characterize the radiation difference between the target and complex background and select the detection bands. The simulation experiment shows that the modified SCR improves over three orders of magnitude compared with the traditional performance characterization methods under different backgrounds.

Flexible thermal strap is a key component for space optical system to realize cold transfer, insulate vibration. The thermal link based on high thermal conductivity graphene film becomes a hot spot for this application. In order to reduce the loss in the heat transfer process, a study on the heat transfer performance and structural form of the thermal link made by pyrolytic graphite films (PGF) is carried out, the thermal resistance network model of the thermal strap is analyzed, the relationship between the heat transfer, the heat transfer temperature difference at the mounting surface and the number of graphite film layers is established by combining theoretical analysis and DOE design methods. A method for quickly determining the design parameters of the thermal strap is proposed. The PGF thermal strap designed according to this method achieves a small temperature difference which less than 1.7K between the cold tip and the simulated optical bench coupling surface, a length of 117mm for the strap, and a weight of only 60g, when it used to transfer 5W cooling capacity at 200K.

Compared with traditional remote sensing images, hyperspectral images have the advantages of high spectral resolution, combining images with spectrum, and continuous spectrum. The phenomenon of mixed pixels in hyperspectral images seriously affects the accuracy of distinguishing objects on the ground, and has always been an important problem that hinders the further development of this technology. The most effective way to solve the mixed pixel problem is to perform mixed pixel unmixing. The purpose of hyperspectral unmixing is to obtain pure spectrum (endmembers) and their corresponding proportions (abundance). The nonnegative matrix factorization (NMF) technique has been widely adopted in the hyperspectral images unmixing problem due to its own advantages. The NMF method based on sparsity constraint can achieve better unmixing effect because of fully using of the sparse characteristic of the data. However, the unmixing model based on the sparse NMF still has shortcomings. Hyperspectral images contain a large amount of geometric structural information, which is not considered by most existing sparse NMF methods. To address those shortcomings, new regularization terms and weights can be introduced into the NMF model to better promote the unmixing performance. To solve this problem, a novel unmixing algorithm named spatial-spectral graph regularized sparse non-negative matrix factorization (SSGNMF) algorithm is proposed in this paper. Most of the sparse constrained unmixing algorithms have the problem of insufficient prior representation of abundance sparsity and using of spatial information insufficiently. On the one hand, the model of SSGNMF introduces graph regularization to preserve high-dimensional spatial information in hyperspectral images. On the other hand, the spatial weighting factor enables more spatial information to be incorporated into the unmixing model, and the spectral weighting factor can promote row sparsity of abundance matrices. By comparing with other classical algorithms, simulated and real hyperspectral data experimental results demonstrate that the introduction of dual weights and graph regularization can improve the unmixing effect, which verifies the validity of this algorithm. In addition, the experimental results also show that the graph regularization term and dual weights introduced in the NMF model in this paper can indeed promote the hyperspectral image unmixing performance well.

The space-borne infrared (IR) hyperspectral sounder is one important part of benchmark instruments for detection of the tiny change of long-term global climate. The IR sounder should provide irrefutable benchmarking records by measuring the infrared radiance with an ultra-high accuracy of 0.1 K (k=3, or 99% confidence), and tracing it to the Système Internationale (SI) standard for the Kelvin through the Planck function theory. Besides, the IR sounder would also constitute a reference standard, or calibration observatory, in space to inter-calibrate the international fleet of IR sounders onboard weather satellites, especially those are not as well calibrated. The measurement needs to be well-calibrated with the instrument features being eliminated, and it is critical to investigate the possible error sources associated with the sounder design and its radiometric calibration. One calibration error that arises in Fourier Transform Spectrometers (FTS) has been found associated with the spectrally variable instrument responsivity. According to the theoretical analysis of the current radiometric calibration, this error is an intrinsic feature of the FTS instruments, but it will lead to the measurements no longer being served as the standard radiances because of a radiance error introduced in the calibrated spectrum. In this paper, the radiometric errors result from the instrument responsivity effect are revealed by numerical simulations based on the spectral responses for ideal and close-to-real instruments.

The line error band models have been extensively used for evaluating the position errors of the line features in surveying, remote sensing, etc.. Although there have been several classical line error band models, the shapes and the probabilities of those models have not been unified. In this paper, the probabilities of line segment falling in its several representative line error bands, namely ε-band, G-band and standard deviation band, are estimated though simulated experiments. A probability-related evaluation index is proposed to evaluate the error models with the aim to provide suggestions for selection of different error models in various scenarios.

The targets of landing missions on small celestial bodies usually have high scientific value but complex terrain. Therefore, there are high demands for the landing trajectory planning method with regard to the safety and precise landing. The artificial potential function method is one of the commonly used methods in trajectory planning for small celestial body landing. It is performed by applying attractive force form the target and repulsive force from the obstacles to the moving spacecraft. The attractive and repulsive forces are generated by the corresponding potential functions, which involves several parameters needed to be determined. Improper parameters may lead to low efficiency of trajectory calculation, collision with obstacles or failure of reaching the target. However, the parameters in the artificial potential functions are usually set as empirical values without consideration of different application scenarios. In this paper, the setting methods of the weight matrices 𝑃_𝑟 and 𝑃_𝑉 in the attractive potential function, the parameter matrix 𝛭 in the Lyapunov function and the parameters 𝑘₁ and 𝑘₂ in the Gaussian-type repulsive potential function are studied, and several simulation experiments are conducted to verify the parameter values. And suggestions are given on the setting of these parameters. Keywords: artificial potential function, parameter setting, landing trajectory planning.

In the infrared detection of small targets, the blind pixels greatly interfere with the detection accuracy of the target. Therefore, the way how to correctly detect and eliminate blind pixels is of great importance. In this paper, an in-orbit real-time blind pixel detection method that combines the time-domain noise of imaging sensor and the characteristics of non-uniform correction coefficients is proposed. Firstly, according to the in-orbit working condition of the remote sensing camera, the imaging data of the reference source that under high and low temperature circumstances is acquired, and the pixels of which the noise exceeds the threshold are marked out through the real-time analysis of time-domain noise of the imaging data. Secondly, a time domain filter is applied to the imaging data of both high temperature reference source and low temperature reference source to reduce noise interference. The two-point correction is then implemented on the filtered imaging data to obtain the gain correction coefficient and the offset correction coefficient of each pixel, and a limitation process is given on the pixel coefficients which are beyond range of bit width or cannot be corrected by hardware. After that the statistical distribution chart of coefficients is acquired through the statistical analysis of the gain coefficient and offset coefficient of all pixels, and according to the statistical characteristic value “μ” and “σ”, the pixels of which the distribution of its coefficients exceeds “±3σ” boundary are marked out. Finally, seeking the union of the two marking position sets, and the marking position of the “union” indicates the coordinate position of the blind pixel detected in real time in orbit. The method proposed in this paper takes the use of the in-orbit calibration mode of the remote sensing camera to realize the in-orbit real-time detection of blind pixels, which made a superiority of this method in identification accuracy comparing to the laboratory reference-source based blind pixel detection method, as the imaging mode and the environmental circumstance of the camera are based on actual working condition. Moreover, comparing to the scene-based detection methods, this method proposed proceeds before ground imaging, which means it does not lead to the misjudgment of infrared small targets to blind pixels. According to the experiment data comparison, the method proposed in this paper provides a matching rate of blind pixel identification of above 90% to the result obtained through the way of the Military Standard of China under the same condition, which demonstrates it has the capability to be widely applied to the infrared remote sensing cameras that have reference-source attached.

The structure of a space electric cabinet based on a commercial CMOS chip is presented. Analysis is conducted according to the temperature specifications and the environmental constraints, which indicates the partitional thermal control method has higher energy efficiency than conventional TEC cooling. A flexible graphite thermal cable is used to build an independent cooling path for the focal plane component. The camera hood is utilized to cool down the peripheral circuit. Copper sinks are designed for high power electronic components. The thermal control design is verified by finite element simulation analysis and thermal balance test. The experimental results show that the partitional thermal control measures are effective and feasible, which can ensure the -30°C operating temperature of CMOS chip and the derating requirements of components with high power consumption.

Alteration information is an important prospecting element in the exploration of deep earth resources. Hyperspectral technology has unique advantages in fine detection and inversion of altered mineral information. Drill core spectral scanning based on hyperspectral technology can identify mineral information in cores nondestructively, rapidly and in batches, which provides an effective means for revealing deep alteration information and its distribution characteristics. In this paper, we use this technology to study the alteration types and combination characteristics of the underground space of the typical deposit in the Kalatag ore collection area, as well as the distribution characteristics of the three-dimensional space of alteration information, and obtain the alteration mineral types and their relative content cataloguing curves of the 10,000 meter drilled cores in different exploration lines. The drill core in the mining area can be divided into three main alteration zones from the shallow part to the deep part, combined with the analysis of the geological core catalogue data. The upper zone is dominated by iron oxide, gypsum and aluminum-sericite. The middle zone is mainly composed of medium aluminum sericite, chlorite, and montmorillonite, with a small amount of high aluminum sericite and iron oxide compounds. In the lower zone, the altered minerals are dominated by high-alumina sericite and chlorite, with a small amount of medium-aluminum sericite and carbonate, as well as sericite and chlorite show obvious negative correlation. There are significantly different types of altered minerals, mineral assemblage characteristics and alteration scale in each alteration zone and between the zones, which reflects that the mineral generation environment has obvious differences with the change of drilling depth. Comprehensive research based on the differences of mineral formation environments can provide important support for deep exploration of underground alteration spatial characteristics, redox zoning, inversion of hydrothermal fluid characteristics and comprehensive analysis of metallogenic environments.