Abstract:This study introduces a comprehensive theoretical framework for accurately calculating the electronic band-structure of strained long-wavelength InAs/GaSb type-II superlattices. Utilizing an eight-band Hamiltonian in conjunction with a scattering matrix method， the model effectively incorporates quantum confinement， strain effects， and interface states. This robust and numerically stable approach achieves exceptional agreement with experimental data， offering a reliable tool for analyzing and engineering the band structure of complex multilayer systems.

Abstract:In order to meet the urgent need of infrared search and track applications for accurate identification and positioning of infrared guidance aircraft， an active-detection mid-wave infrared search and track system （ADMWIRSTS） based on "cat-eye effect" was developed. The ADMWIRSTS mainly consists of both a light beam control subsystem and an infrared search and track subsystem. The light beam control subsystem uses an integrated opto-mechanical two-dimensional pointing mirror to realize the control function of the azimuth and pitch directions of the system， which can cover the whole airspace range of 360°×90°. The infrared search and track subsystem uses two mid-wave infrared cooled 640×512 focal plane detectors for co-aperture beam expanding， infrared and illumination laser beam combining， infrared search， and two-stage track opto-mechanical design. In this work，the system integration design and structural finite-element analysis were conducted， the search imaging and two-stage track imaging for external scenes were performed， and the active-detection technologies were experimentally verified in the laboratory. The experimental investigation results show that the system can realize the infrared search and track imaging and the accurate identification and positioning of the mid-wave infrared guidance or infrared detection system through the echo of the illumination laser. The aforementioned work has important technical significance and practical application value for the development of compactly-integrated high-precision infrared search and track and laser suppression system， and has broad application prospects in the protection of equipment， assets and infrastructures.

Abstract:The performance of detectors is one of the key factors for space target detection. In this paper, the performance requirements of blocked impurity band detectors for the ground-based detection scenario of space targets are analyzed. The theoretical calculation of background radiation and point target radiation is carried out by establishing the radiation transmission model of ground-based detection scenario. The correlation between radiation and detector performance is also analyzed. Taking space debris as a typical target and ground-based telescope as a carrying platform, the key performance requirements such as quantum efficiency, dark current, full well and specific detectivity are analyzed and calculated in the mid-latitude and high-altitude detection environment. This work lays a theoretical foundation for the detector structure design of ground-based detection.

Abstract:The application of InGaAs focal plane arrays （FPAs） desires high density and small pixel pitch， and the smaller the pixel pitch， the stronger the pixel coupling. By fabricating 5 μm pitch InGaAs arrays with different scales， the pixel coupling effects in high-density InGaAs arrays were studied. Innovatively， matrix equations were introduced to describe the contributions of dark current from each part， constructing a mathematical model of pixel coupling and the contributions of dark current resulting from coupling effects were quantitatively analyzed. The results indicated that at a bias voltage of -0.1 V， the reverse-biased pixels in the array can suppress the dark current of adjacent reverse-biased pixels by 21.39% of the pixel"s initial dark current. In contrast， zero-biased pixels can increase the dark current of adjacent reverse-biased pixels by 219.42%. Based on the high-density focal plane pixel coupling model， the impact rules of pixel coupling on dark current have been summarized， providing new insights for the dark current research in high-density InGaAs focal plane arrays.

Abstract:The thermal load of the cryogenic infrared detector Dewar is a comprehensive indicator characterizing the adiabatic capacity of the Dewar. Radiative heat is a part of the thermal load. When calculating the radiative heat ，the traditional approach typically simplifies the Dewar to a coaxial cylindrical model. This simplified model differs significantly from the actual one and the traditional approach is incapable of computing the radiative heat transfer between surfaces where emissivity， transmittance， and reflectance vary with wavelength. To enhance the calculation accuracy of the Dewar"s radiative heat， based on the Monte Carlo principle， a 3D Studio Max modeling was employed， model information was extracted， and a program was developed， resulting in a set of general calculation programs for the Dewar"s radiative heat based on the radiation transfer factor. To preliminarily verify the accuracy of the calculation program， the cold side radiative heat of two types of experimental dewars was calculated according to the gray body assumption and compared with the measured values. The theoretical calculated value and measured value of the cold side radiation heat of experimental dewar 1 were 155 mW and 136 mW， respectively， with an error of 19 mW； the theoretical calculated value and measured value of cold side radiation heat of experimental dewar 2 were 87 mW and 79 mW， respectively， with an error of 8 mW. After initially testing the accuracy of the calculation program， the cold side radiative heat of an engineering typical 1K×1K long-wave dewar when the emissivity of the window facing it was 0.9 was calculated and measured experimentally. The theoretical calculated value was 127 mW， and the measured value was 110 mW， with an error of 17 mW.

Abstract:A transceiver module operating at the 220 GHz frequency band was developed， consisting of three parts： a local oscillator chain， a transmitter chain， and a receiver chain， featuring high integration. A 218~226 GHz waveguide bandpass filter was designed to suppress spurious signals in the chain. The filter adopts a dual-mode resonant cavity structure to introduce a transmission zero on the left side of the passband， which suppresses the 214 GHz spurious signal by 60 dBc. An improved E-plane magic-T structure was used to form a four-way power combining amplifier to meet the requirement of transmit power. This module achieves a power combining efficiency of 72.5% and the output power is higher than 82 mW. The measured results show that in the 219.5~221 GHz frequency range， the transmit power is 82~95 mW， the noise figure of the receiver is less than 7.1 dB， the receive gain is 5.1~6.0 dB， and the volume of module is 65×70×30 mm3.

Abstract:Self-supervised pre-training methods have strong capabilities in feature extraction and model transfer. However， current pre-training methods in multimodal remote sensing image （RSI） fusion only perform simple fusion operations such as concatenation on the extracted multimodal features without designing dedicated modules for the integration of multimodal information， leading to insufficient fusion of complementary information across modalities. Secondly， these methods do not consider and utilize the cross-scale consistency priors within RSIs， resulting in limited extraction and integration of multimodal remote sensing information， and thus the performance of various downstream tasks needs to be improved. In response to the above issues， a multimodal RSI fusion method based on self-supervised pre-training and cross-scale contrastive learning is proposed， which mainly includes three parts： 1） By introducing a cross-attention fusion mechanism to preliminarily integrate features extracted from different modalities， and then using encoder modules to further extract features， explicit aggregation and extraction of complementary information from each modality are achieved； 2） By introducing a cross-modality fusion mechanism， each modality can extract useful supplementary information from the features of all modalities， and reconstruct each modality’s input after separate decoding； 3） Based on the cross-scale consistency constraints of RSIs， cross-scale contrastive learning is introduced to enhance the extraction of single-modality information， achieving more robust pre-training. Experimental results on multiple public multimodal RSI fusion datasets demonstrate that， compared with existing methods， the proposed algorithm has achieved significant performance improvements in various downstream tasks. On the Globe230k dataset， our method achieves an average intersection over union （mIoU） of 79.01%， an overall accuracy （OA） of 92.56%， and an average F1 score （mF1） of 88.05%， and it has the advantages of good scalability and easy hyperparameter setting.

Abstract:We present the design， simulation， and experimental validation of a InP/In_0.53Ga_0.47As laser power converters for the wavelength of 1550 nm. By optimizing the thickness of the absorption layer and using a double-layer anti-reflection structure （SiO₂ and SiN）， By optimizing the thickness of the absorption layer and adopting a dual-layer anti-reflective structure （SiO₂ and SiN）， the device achieved an absorptance of 96% under 1550 nm laser irradiation， demonstrating insensitivity to angle variation and robust to wavelength shifts. The experimental results are in good agreement with the theoretical calculation results. The external quantum efficiency （EQE） reaches 92%. Under a laser power density of 47 mW/cm2， the cell’s conversion efficiency reached 23%. Further refinement of device processing is needed to reduce series and shunt resistances， thereby enhancing the overall efficiency of the laser photovoltaic cell. In addition， this study delves into the impact of cell area on the photovoltaic performance， providing optimization directions for the miniaturization of laser photovoltaic cells.

Abstract:Airborne area-array whisk-broom imaging systems often adopt constant-speed scanning schemes. For large-inertia scanning systems， constant-speed scanning consumes a significant amount of time to complete the reversal motion， limiting the system"s adaptability to high-speed reversal scanning and restricting scanning efficiency. This study proposed a novel sinusoidal variable-speed roll scanning strategy， which reduced abrupt changes in speed and acceleration， minimizing time loss during reversals. Based on the forward image motion compensation strategy in the pitch direction， a line-of-sight （LOS） position calculation model with vertical flight path correction （VFPC） was established， ensuring that the central LOS of the scanned image remained stable on the same horizontal line， which was conducive to accurate image stitching in whisk-broom imaging. Through theoretical analysis and simulation experiments， the proposed method improved scanning efficiency by approximately 18.6% at a 90° whisk-broom imaging angle under the same speed height ratio conditions. The new VFPC method enables wide-field， high-resolution imaging， achieving single-line LOS horizontal stability with an accuracy better than 0.4 mrad. The research work of this thesis is of great significance to promote the further development of airborne area-array whisk-broom imaging technology toward wider fields of view， higher speed height ratios， and greater scanning efficiency.

Abstract:Based on two-dimensional triangular lattice photonic crystal， a multi-functional device of two-dimensional photonic crystal waveguide light-emitting beaming with integrated filtering function is designed， which can realize the fusion of outgoing light beaming and specific wavelength efficient filtering. The beam structure of the emitting light is similar to the grating structure， and the beam is in the state of clustering through the mutual interference principle between the multi-channel， which improves the radiation efficiency and distance of the emitting light. The finite difference time domain method can be used to obtain the effective propagation distance of 450 at the incident wavelength of 1.447. The structure design has a good beaming ability for incident light in the range of 1.435~1.465. At the same time， there are two hexagonal coupled filtering structures on either side of the waveguide， which are close to 98.4% and 97.3% transmission efficiency for incident light waves with a central wavelength of 1.490 and 1.510， respectively.The fusion structure successfully realizes the filtering and clustering functions.