Abstract:Millimeter-wave （MMW） technology has been widely utilized in human security screening applications due to its superior penetration capabilities through clothing and safety for human exposure. However， existing methods largely rely on fixed polarization modes， neglecting the potential insights from variations in target echoes with respect to incident polarization. This study provides a theoretical analysis of the cross-polarization echo power as a function of the incident polarization angle under linear polarization conditions. Additionally， based on the transmission characteristics of multi-layer medium， we extended the depth spectrum model employed in direct detection to accommodate scenarios involving multi-layered structures. Building on this foundation， by obtaining multiple depth spectrums through polarization angle scanning， we propose the Polarization Angle-Depth Matrix to characterize target across both the polarization angle and depth dimensions in direct detection. Simulations and experimental validations confirm its accuracy and practical value in detecting concealed weapons in human security screening scenarios.

Abstract:Due to the close pixel size and working wavelength of the focal plane polarization integrated infrared detector， diffraction effects cause severe crosstalk between adjacent pixels with different polarized light. A single traditional metal grating structure cannot achieve high extinction ratio polarization detection chips. This article proposes and designs a metasurface lens stacked polarization integrated infrared detector structure， studies the optical field convergence ability of metalens for different wavelengths of infrared light waves， prepares metastructural lenses and submicron grating structures， and integrates them with infrared focal planes. The polarization extinction ratio of the device exceeds 15：1， and dynamic and variable temperature objects are selected for polarization imaging experiments， demonstrating the imaging advantages of polarization integrated devices with focal planes.

Abstract:A whispering gallery mode microsphere resonator is proposed and demonstrated. The device is fabricated by splicing a single-mode fiber with a capillary tube and， by properly adjusting the discharging current and the splicing position of the fiber and capillary tube， an expanded hollow sphere cavity is formed at the splicing junction. A microsphere is inserted into the hollow sphere cavity and positioned in close touch with the cavity wall to excite whispering gallery mode resonance via the coupling of evanescent field of the anti-resonant reflecting guidance mode produced in the cavity wall. The device has a quality factor of 3.725 × 10³ and is compact， simple in fabrication， easy in packaging， convenient in operation and of low cost.

Abstract:High-performance uncooled terahertz （THz） detectors have a wide range of applications in many technological fields， such as high-rate data communications， real-time imaging， spectroscopy and sensing. However room-temperature THz detectors with high sensitivity and fast response capability are still rare. In recent years， the hot-carrier photothermoelectric （PTE） effect in two-dimensional （2D） materials has been found to be useful for room-temperature， high-speed， and highly sensitive photodetection in the THz and long-wave infrared radiation. In this study， the authors constructed a room-temperature THz detector based on the high-performance 2D layered thermoelectric material Bi₂Te₃， which employs a bow-tie antenna as an asymmetric light coupler and utilizes the hot-carrier PTE effect to achieve THz detection in zero-bias mode. The results show that the Bi₂Te detector exhibits excellent THz detection performance， with a responsivity and noise equivalent power （NEP） of 0.45 A/W and 17 pW/Hz^1/2， and a fast response time of 12 μs under 100 GHz radiation， respectively. This work demonstrates the promising application of Bi₂Te₃ THz detectors based on the hot-carrier PTE effect in realizing high-performance uncooled THz detectors.

Abstract:With the widespread application of infrared detection technology in fields such as military reconnaissance， aerospace monitoring， and security early warning， infrared measurement systems play a critical role in infrared detection. In response to issues such as low calibration efficiency and significant environmental interference in the calibration and radiative property inversion of infrared measurement systems， this paper proposes a calibration and radiative property inversion method based on infrared weak small targets. A small-area blackbody source is used as a controllable radiation source to project infrared targets， and deep learning networks are employed for precise identification and gray-scale extraction of infrared weak small targets. Using this， a calibration model for the measurement system is established. Experimental results show that the method demonstrates good calibration stability within the temperature range of 298 K-308 K， with the absolute error of radiative property inversion controlled within ±2 K and the relative error of inversion temperature ≤ 0.5%. Regression analysis also indicates high temperature inversion accuracy （R2>0.94）. Compared to traditional methods， the proposed method balances calibration efficiency and accuracy while extending the ability to invert the temperature field of targets. This research provides an effective solution for rapid calibration and high-precision radiative property analysis of infrared weak small targets.

Abstract:The study simulated imaging characteristics of a segmented planar imaging system. It investigated the influence of structural parameters on imaging results based on a checkerboard lens sampling array， and provided optimal parameters for the system. The work innovatively employed hyperspectral images to analyze the impact of interference spectral width on imaging quality in natural scenes， concluding that the allowable interference bandwidth in practical applications should not exceed 100 nm. The discussion on allowable bandwidth and error analysis based on real-world scenarios offered guidance for developing checkerboard-type imagers. These findings also provided universal insights applicable to all segmented planar imaging systems.

Abstract:InAs/GaInSb Type-II superlattice （T2SL） materials exhibit significant advantages in long-wavelength （LWIR） and very long-wavelength infrared （VLWIR） detectors. By optimizing molecular beam epitaxy （MBE） growth parameters and interface control techniques， a 50-period short-period superlattice （SL） structure composed of 10-monolayer （ML） InAs/7ML Ga_0.75In_0.25Sb was successfully grown at the GaSb reconstruction transition temperature. High-resolution X-ray diffraction （HRXRD） characterization revealed a lattice constant of 6.108 ? and a period thickness of 53.53 ? for the superlattice， with deviations from theoretical design values below 0.2%. The lattice mismatch with the GaSb substrate was only 0.197%. Atomic force microscopy （AFM） measurements demonstrated a root mean square （RMS） surface roughness of 1.67 ?， while photoluminescence （PL） spectroscopy indicated a bandgap of 89.9 meV. Furthermore， a 12ML InAs/5ML Al_0.8In_0.2Sb superlattice barrier material was epitaxially grown， exhibiting a lattice mismatch of 0.067% with the GaSb substrate. Experimental results confirm that both the 10ML InAs/7ML Ga_0.75In_0.25Sb and 12ML InAs/5ML Al_0.8In_0.2Sb superlattices exhibit excellent lattice compatibility with the GaSb substrate. The presence of multiple satellite diffraction peaks and superior interface quality further validate the structural integrity of the materials. These findings provide a critical material foundation for the development of high-performance infrared detectors.

Abstract:The superlattice long-wavelength infrared focal plane detectors operate at low-temperatures. The differences in the thermal expansion coefficients among the various material layers of the detectors can lead to deformation and generate thermal stress， which in turn affects the optoelectrical performances of the detector. This study designed two structural modules to achieve the regulation of stress in the superlattice detectors. The changes in dark current and spectral response of InAs/GaSb type II superlattice long-wave infrared focal plane detectors under different stress conditions were explored. The research indicates that within the stress range of -10.7 MPa to 131.9 MPa， the variations in the optoelectrical performance of the detector is small. The detector was subjected to a temperature shock test， and it demonstrated high reliability. Our research results provide guidance for the structural design of InAs/GaSb type II superlattice long-wave infrared focal plane detectors and offer a basis for their performance and reliability assessment.

Abstract:We demonstrate terahertz quantum cascade （THz-QC） wire lasers based on dual coupled gratings that achieve continuous-wave （CW） operation near liquid nitrogen temperatures with a low-divergence Gaussian-like beam profile. Our configuration circumvents the effective refractive index constraint， significantly enhancing fabrication efficiency while retaining the key advantages of low power consumption and high heat dissipation efficiency. By engineering the photonic band structure of the coupled gratings， the laser operates on two supermodes. For Supermode #1， grating 1 serves as the master oscillator while grating 2 functions as a phased antenna array， featuring a collimated beam. For Supermode #2， grating 2 is the main oscillator and simultaneously provides a collimated beam， while grating 1 offers high reflectivity. Both supermodes exhibit high cavity quality factors and low beam divergence， achieved with a significantly reduced gain area. Experimentally， both supermodes were observed， and the optimized laser produces a collimated Gaussian beam with divergence angles of 12°×18° and an optical power of 1.04 mW. The threshold power consumption and thermal resistance are as low as 2.62 W and 8.5 mK/W/cm2， respectively， resulting in a maximum CW operating temperature of 78.0 K. This work offers a more accessible route for low-divergence， low-power-consumption， high-thermal-dissipation-efficiency THz-QCLs with enhanced CW operation at elevated temperatures.

Abstract:Photocurrent scanning imaging （mapping） technology is a key technique in the research of solar cells and photodetectors. However， traditional galvanometer-driven beam scanning methods are limited by a restricted scanning range and image distortion. To address these shortcomings and meet the need for testing the photocurrent uniformity of large-area optoelectronic devices， an automated photocurrent mapping testing system has been developed based on optical component scanning. This system offers a large imaging range， high spatial resolution， high stability， and low cost. With its high-precision mode， it can achieve sub-micron geometric positioning （subdivision number 6400， scanning step size 0.625 μm）， fulfilling both large-area scanning requirements and providing high-resolution testing. Moreover， its simple structure greatly reduces the overall cost of the mapping system. Using a silicon solar cell sample with surface covered by a “南” （south） character paper or a encoder strip mask， it was demonstrated that the scanning range exceeds 10×10 mm2， with a spatial resolution of 0.6 μm. The system was also used to characterize the surface photocurrent images of Cu?ZnSnS? and Cu?ZnSn（S，Se）? solar cells. The results show that the Cu?ZnSnS? cell contains more defects， while the Cu?ZnSn（S，Se）? cell exhibits a more uniform surface photocurrent response with fewer defects. These findings contribute to the optimization of solar cell fabrication processes.