Abstract:Silicon （Si） diffraction microlens arrays are usually used to integrate with infrared focal plane arrays （IRFPAs） to improve their performance. The errors of lithography are unavoidable in the process of the Si diffraction microlens arrays preparation in the conventional engraving method. It has a serious impact on its performance and subsequent applications. In response to the problem of errors of Si diffraction microlens arrays in the conventional method， a novel self-alignment method for high precision Si diffraction microlens arrays preparation is proposed. The accuracy of the Si diffractive microlens arrays preparation is determined by the accuracy of the first lithography mask in the novel self-alignment method. In the subsequent etching， the etched area will be protected by the mask layer and the sacrifice layer or the protective layer. The unprotection area is carved to effectively block the non-etching areas， accurately etch the etching area required， and solve the problem of errors. The high precision Si diffraction microlens arrays are obtained by the novel self-alignment method and the diffraction efficiency could reach 92.6%. After integrating with IRFPAs， the average blackbody responsity increased by 8.3%， and the average blackbody detectivity increased by 10.3%. It indicates that the Si diffraction microlens arrays can improve the filling factor and reduce the crosstalk of IRFPAs through convergence， thereby improving the performance of IRFPAs. The results are of great reference significance for improving their performance through optimizing the preparation level of micro nano devices.

Abstract:The development of InGaAs/InP single-photon avalanche photodiodes （SPADs） necessitates the utilization of a two-element diffusion technique to achieve accurate manipulation of the multiplication width and the distribution of its electric field. Regarding the issue of accurately predicting the depth of diffusion in InGaAs/InP SPAD， simulation analysis and device development were carried out， focusing on the dual diffusion behavior of zinc atoms. A formula of to quantitatively predict the diffusion depth is obtained by fitting the simulated twice-diffusion depths based on a two-dimensional （2D） model. The 2D impurity morphologies and the one-dimensional impurity profiles for the dual-diffused region are characterized by using scanning electron microscopy and secondary ion mass spectrometry as a function of the diffusion depth， respectively. InGaAs/InP SPAD devices with different dual-diffusion conditions are also fabricated， which show breakdown behaviors are well consistent with the simulated results under the same junction geometries. The dark count rate （DCR） of the device decreased as the multiplication width increased， as indicated by the results. DCRs of 210⁶， 110⁵， 410⁴， and 210⁴ were achieved at temperatures of 300 K， 273 K， 263 K， and 253 K， respectively， with a bias voltage of 3 V， when the multiplication width was 1.5 μm. These results demonstrate an effective prediction route for accurately controlling the dual-diffused zinc junction geometry in InP-based planar device processing.

Abstract:Metasurfaces in the long wave infrared （LWIR） spectrum hold great potential for applications in thermal imaging， atmospheric remote sensing， and target identification， among others. In this study， we designed and experimentally demonstrated a 4 mm size， all-silicon metasurface metalens with large depth of focus operational across a broadband range from 9 μm to 11.5 μm. The experimental results confirm effective focusing and imaging capabilities of the metalens in LWIR region， thus paving the way for practical LWIR applications of metalens technology.

Abstract:Variable optical attenuator （VOA） arrays can be widely applied in optical communication and optoelectronic systems， but few VOA arrays are reported. Here a liquid-stop based microfluidic VOA array is proposed. It uses a spiral orbit to achieve different degrees of synchronous energy attenuation of multiple beams， or uses an annular orbit to achieve a same degree of synchronous energy attenuations， where the clear aperture of liquid stop is regulated by the electrowetting-on-dielectric effect. It has a compact structure， small volume， simple operation and low cost. Meanwhile， the attenuation ratio of beams can be flexibly adjusted to achieve the power equalization. The research results indicate that the VOA array has a wide attenuation range （0-100% attenuation） and very small insertion loss （0.26 dB） over general VOA arrays. The response time is 0.1 ms， and it is insensitive to the polarization. It can also act as an optical switch array. The proposed VOA array demonstrates the potential of integration and high performance， and it can provide a cost-effective way for applications.

Abstract:Photoreflectance （PR） has been widely used for the characterization of various semiconductors as well as their surface and interface properties due to its non-destructive and high sensitivity virtues. From the viewpoint of the employment of monochromator， the experimental setup may be classified into dark and bright configurations， which were applied to characterize the heterostructure of InP/In_0.52Ga_0.48As/InP grown by molecular beam epitaxy. It reveals that the front configuration well separates the luminescence from the modulation signal while the backside configuration benefits the extraction of weak modulation signals with the employment of high excitation power. Based on the backside configuration， we also observed a below band-gap excitation phenomenon， i.e. that the modulation signal of InP exhibits under the excitation of energetically low modulation light （1 064 nm laser）. The result demonstrates that the backside configuration may be employed as a contactless electro-modulation technique for the characterization of wide band gap semiconductor heterostructures.

Abstract:As the cell size of uncooled infrared （IR） detectors progressively shrinks， it becomes increasingly important to increase detector absorption. here， an IMIAM （Insulator-Metal-Insulator-Air-Metal） cavity type metasurface uncooled IR detector structure is proposed， which effectively improves the uniformity of the photosensitive layer while enhancing the absorption of the detector. Utilizing systematic simulation and optimization， it has achieved almost perfect absorption in the Long Wavelength Infrared range （8~14 μm）， meanwhile， it also shows excellent absorption performance in Mid Wavelength Infrared band. In this paper， the reliability of the structure is also verified by the process. this research may provide alternatives for optimizing conventional uncooled IR detectors

Abstract:In this paper， a dual-band graphene-based frequency selective surface （GFSS） is investigated and the operating mechanism of this GFSS is analyzed. By adjusting the bias voltage to control the graphene chemical potential between 0 eV and 0.5 eV， the GFSS can achieve four working states： dual-band passband， high-pass low-impedance， low-pass high-impedance， and band-stop. Based on this GFSS， a hexagonal radome on a broadband omnidirectional monopole antenna is proposed， which can achieve independent 360° six-beam omnidirectional scanning at 1.08 THz and 1.58 THz dual bands. In addition， while increasing the directionality， the peak gains of the dual bands reach 7.44 dBi and 6.67 dBi， respectively. This work provides a simple method for realizing multi-band terahertz multi-beam reconfigurable antennas.

Abstract:To meet the high-speed and high-capacity demands of communication， a 300GHz electronic wireless transmission system for terahertz frequencies is proposed， which incorporates Probability Shaping （PS）， Discrete Multi-tone Modulation （DMT） and DFT-Spread （DFT-S） techniques. PS increases the Euclidean distance between constellation points， thereby enhancing the receiver sensitivity. In the system at most 55% bit error rate is decreased， enabling to extend transmission range. DFT-S technique reduces 1.68 dB peak-to-average power ratio of Orthogonal Frequency Division Multiplexing （OFDM） signals in the system， thus improving their resistance to nonlinear effects. By integrating these advanced digital signal processing techniques， 12GBaud PS-16QAM OFDM-DMT signals and 10GBaud PS-64QAM DFT-S-OFDM-DMT signals were successfully implemented in 1 m wireless transmission. Finally， the performance advantages of these digital signal processing techniques were compared.

Abstract:Terahertz （THz） technology is undergoing a rapid development in biomedical applications. Researchers have made a series of important achievements in the study of biological samples on various levels such as biomolecules， cells， tissues， and individual organisms， which provide new insights and innovative approaches for biological research and biomedical diagnosis. In this review， the progress of applying THz technology in biomedical studies has been summarized， including three key aspects， namely， spectroscopic detection， imaging， and biological effects. The challenges encountered in THz biomedical applications have been discussed， and the future development directions have also been envisioned.

Abstract:The variations in extinction and microphysical properties in the upper haze of Venus have a significant impact on the chemistry and radiative balance of its atmosphere. In order to study their spatial and temporal distribution， we analyzed solar occultation data from the Venus Express SPICAV SOIR instruments between 2006 and 2013. To remove the absorption effects of the middle and upper atmosphere of Venus， we used MODTRAN modeling. Then， we retrieved the extinction profiles of the upper haze between 67-92 km using the onion-peeling method. Our findings are as follows： 1） The extinction coefficient of the upper haze generally decreases with increasing altitude， but there are significant variations between different regions. In low latitudes， the extinction increased sharply early in the mission， and the average extinction coefficient of the haze showed minimal changes between day and night. The vertical optical depth of the haze layer was approximately 10^-2. 2） The number density of the upper haze decreases with increasing altitude. From the south to the north pole， the number density first increases and then decreases. 3） The cloud top altitude is higher in low-latitude regions at 82.7 ± 5.8 km， while in polar regions， it is lower with the northern polar region at 73.3 ± 2.4 km and the southern polar region at 79.5 ± 3.5 km. The average scale height of the upper haze layer in the northern polar region is 4.0 ± 0.9 km.

Abstract:Optical coherence tomography （OCT） technology has the advantages of non-invasive， high-resolution， and real-time imaging， which is widely used in various fields such as biomedicine， material science and infrared sensing. A ridge suspended optical waveguide based on silicon nitride （Si₃N₄） is proposed. The structural parameters of the designed waveguide were optimized by using finite difference time domain （FDTD） method. The characteristics of the supercontinuum spectrum generated in the optimized waveguide were investigated The simulation results show that for the optimized optical waveguide structure with ridge width of 750 nm， ridge height of 700nm， plate thickness of 200 nm， and upper layer height of 150 nm， when a pump light with wavelength of 1.3μm， peak power of 2 kW and pulse width of 50 fs was injected into the waveguide， a broadband supercontinuum spectrum with wavelength covering the visible to the mid-infrared region （703~4014 nm） can be generated. This work plays an important role in promoting the application of on-chip integrated broadband light source in biomedical imaging and related fields.

Abstract:Remote sensing image scene classification aims to automatically assign a semantic label to each remote sensing image according to its content， and has become one of the hot topics in the field of remote sensing image processing. Methods based on convolutional neural networks （CNNs） and methods based on self-attention mechanism are two mainstream methods in remote sensing image scene classification. However， the former is less effective in exploring long-range contextual information， and the latter has limitations in learning local information and has a large number of parameters and calculations. In order to address these issues， a lightweight method based on knowledge distillation is proposed to solve the problem of scene classification for remote sensing images. The proposed method uses Swin Transformer and lightweight CNNs as the teacher model and the student models， respectively， and integrates the advantages of the two kinds of models by means of knowledge distillation. Furthermore， a novel distillation loss function is proposed to enable the student models to focus on both inter- and intra-class potential information of remote sensing images simultaneously. The experimental results on two large-scale remote sensing image datasets demonstrate that the proposed method not only achieves high classification accuracy compared to existing methods but also has a significantly reduced number of parameters and calculations.

Abstract:High-precision space debris measurements can provide more accurate real-time information on debris targets and enhance the effectiveness of satellite avoidance warnings for space debris. Through the modification of the 1.2 m aperture quantum communication telescope （altitude 3200 m） in Qinghai Province， the satellite laser ranging （SLR） and space debris laser ranging （DLR） experiments were carried out by using a single pulse energy of 1.2 mJ and a repetition rate of 1 kHz picosecond laser， in which the detection range of cooperative satellites has been extended from Low Earth Orbit to Geosynchronous Eearth Orbit， and the ranging accuracy was better than 2 cm. The maximum distance of space debris target measurement is 1620.5 km， the radar cross section （RCS） is 2.41 m²， and the ranging accuracy reaches 10.64 cm.A single laser system has been realized， which can not only carry out centimeter-level high-precision ranging of cooperative targets， but also realize space debris observation. This is the first time in the world to use high repetition frequency and low power laser ranging system to achieve high precision measurement of space debris targets， reflecting the advantages of picosecond laser and high-altitude large-aperture telescope measurement， providing reference for developing space target laser ranging in western China， and providing an effective way for space debris laser ranging system site selection and space debris monitoring capability enhancement.

Abstract:Through sufficient investigation and summary， the development trend and representative work of Metaverse and related technologies in the aerospace field since the 1960s have been sorted out， and it is pointed out that multi-satellite networking， digitalization and virtualization will become important development trends of aerospace science and technology. Hence， a new concept called “Aerospace Metaverse” has been proposed. Based on this concept， the fundamentals of mathematics and physics have been analyzed. Necessry technologies to build Aerospace Metaverse such as digital twins of aerospace and wide domain ultra high speed intelligent perceptionhave been proposed， and their implementation approaches are elaborated. Furthermore， combining with the vigorous development of aerospace technology， scenarios that can be first put into use have been predicted. Several existing difficulties in building Aerospace Metaverse and corresponding solutions have been proposed， providing new ideas for the development of aerospace technology. Finally， an outlook has been made on the future development of Aerospace Metaverse.

Abstract:The geometric accuracy of topographic mapping with high-resolution remote sensing images is inevitably affected by the orbiter attitude jitter. Therefore， it is necessary to conduct preliminary research on the stereo mapping camera equipped on lunar orbiter before launching. In this work， an imaging simulation method considering the attitude jitter is presented. The impact analysis of different attitude jitter on terrain undulation is conducted by simulating jitter at three attitude angles， respectively. The proposed simulation method is based on the rigorous sensor model， using the lunar digital elevation model （DEM） and orthoimage as reference data. The orbit and attitude of the lunar stereo mapping camera are simulated while considering the attitude jitter. Two-dimensional simulated stereo images are generated according to the position and attitude of the orbiter in a given orbit. Experimental analyses were conducted by the DEM with the simulated stereo image. The simulation imaging results demonstrate that the proposed method can ensure imaging efficiency without losing the accuracy of topographic mapping. The effect of attitude jitter on the stereo mapping accuracy of the simulated images was analyzed through a DEM comparison.