Abstract:Infrared detector has been widely applied in aerospace reconnaissance， electro-optical countermeasures， and space science. Currently， it is undergoing a critical transition from the "full development of the third generation" to the "exploration of the fourth generation." Based on the pressing demands of current infrared detection applications， the preliminary definition and development considerations of the fourth-generation infrared detector was discussed. First， the developmental trajectory of infrared detectors was outlined. The evolution trend of the fourth-generation infrared detectors was explored from the perspectives of function integration， disciplinary advancement， and technology progression， and an initial definition for fourth-generation infrared detectors was proposed. Secondly， the preliminary contemplation on pivotal technological advancements for fourth-generation infrared detectors， encompassing the exploration of extreme detection performance， multidimensional light field information sensing， on-chip intelligence， and infrared microsystem chips， was delineated. Finally， an intelligent manufacturing ecosystem for infrared detectors was envisaged， which facilitates the transition of fourth-generation infrared detectors from conceptualization to practical application.

Abstract:This study presents the design， fabrication， characterization， and testing methodology of a reflective blazed grating operating in the Littrow configuration. The grating， fabricated via mechanical ruling with a sawtooth profile， was characterized using a terahertz quantum cascade laser combined with self-mixing interferometry. Non-contact measurements yielded a grating constant of 84.89 μm and a blaze angle of 24.9°， with performance metrics including an angular resolution of 0.117 rad/THz and a peak diffraction efficiency of 71% within the terahertz band， consistent with theoretical predictions. By directly resolving grating parameters through laser feedback signals， this method significantly improved measurement speed compared to conventional approaches， demonstrating potential for real-time dynamic characterization of grating devices.

Abstract:In order to investigate the electrical properties of InAs/GaSb type-II superlattices， a lattice-matched AlAsSb electrical isolation layer was grown between the GaSb substrate and the InAs/GaSb type-II superlattice epitaxial material to suppress the conductive effect of the substrate. Temperature-dependent Hall measurements revealed that the undoped superlattice exhibited N-type conductivity. As the P-type doping concentration increased， a compensation doping phenomenon was observed， with the occurrence of conductivity type transitions at 95 K and 230 K， respectively. Below the transition temperatures， P-type conductivity was exhibited， while above the transition temperatures， the material exhibited N-type conductivity. The phenomenon was analyzed using the Fermi level model， and the results indicated that the transition temperature for conductivity type changes increased with increasing doping concentration.

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.