Abstract:Stirling-cooled infrared focal plane detector modules, characterized by their compact size, low power consumption, and high reliability, are widely used in various infrared systems. Among them, long-range missile weapon systems have high requirements on the startup time of guided operations, but existing infrared focal plane detectors are difficult to meet the corresponding needs. By analyzing the key factors influencing the startup time of infrared focal plane detectors, a novel design approach is proposed. While maintaining the original performance of the detector chip and the detector′s optical, mechanical, and electrical interfaces, a micro-dewar, cryocooler, and drive controller are employed to achieve rapid startup. Experimental results show that the new detector design achieves a cooling time of less than 210 seconds at room temperature. Compared with conventional designs, this design significantly shortens the startup time, meeting project requirements and providing a novel solution for the application of infrared focal plane detectors in missile weapon systems.

Abstract:As the application of infrared detectors expands, higher requirements are placed on device weight, volume, heat dissipation, and application scenarios. This paper describes a high-operating temperature HgCdTe long-wave infrared detector with large charge handling capacity. Based on capacitance integration multiplexing, the device achieves a charge handling capacity of 27.2 Me^- at a 15 μm pixel size. The device performance at different operating temperatures is also analyzed. Results show that at 77 K, the device exhibits exceptional performance, with an effective pixel rate of 99.5%, a rear cutoff wavelength of 8.6 μm, a noise equivalent temperature difference (NETD) of 22 mK, and a peak quantum efficiency of 65%. As the operating temperature increases to 110 K, the effective pixel rate reaches 98.5%, with a rear cutoff wavelength of 8.1 μm, a NETD of 28 mK, and a peak quantum efficiency of 40%, achieving a state-of-the-art p-on-n type HgCdTe long-wave infrared detector. This research provides guidance for the fabrication of future high operating temperature devices.

Abstract:To minimize the impact of defects in mercury cadmium telluride (MCT) thin films grown by liquid phase epitaxy (LPE) on infrared detector performance, a special surface defect (the frustum-shaped defect) is systematically studied using a variety of characterization methods, including scanning electron microscope (SEM), energy-dispersive X-ray spectrometer (EDX), and focused ion beam (FIB), combined with comparative experiments. These defects range in size from 150 μm to 400 μm and appear as a concave frustum-shaped morphology under an optical microscope. Compositional analysis reveals no significant differences in composition between the defect surface and the film surface without defects. Analysis of the interface between the cadmium zinc telluride (CZT) substrate and the MCT epitaxial layer confirms that the defect is a through-hole defect, originating from triangular tellurium inclusions with holes in the center of the CZT substrate. The tellurium inclusions are almost always larger than 20 μm in size. Therefore, by improving the quality of the CZT substrate and optimizing the substrate screening process, it is possible to effectively reduce the frustum-shaped defects in MCT thin films, improve the quality of the epitaxial material, and meet the development needs of high-performance infrared detectors.

Abstract:The difference-frequency module is the core component of a tunable terahertz source, and its performance directly affects the efficiency of terahertz wave generation. To increase terahertz output power, 2:1 and 3:1 laser beam reduction systems are designed based on the laser parameters after optical power amplification. This ensures that the spot diameters of the two laser beams are consistent, optimizing the beam combining effect. Polarization calibration is used to maintain horizontal linear polarization of the lasers, thereby fully utilizing the maximum nonlinear coefficient of the crystal. After laser beam combining debugging, the two laser beams can be well combined, and after focusing, a spot with a diameter of approximately 22 μm can be formed, effectively enhancing the difference-frequency effect. Experimental results show that this module has successfully enabled terahertz wave generation.

Abstract:To improve the efficiency and accuracy of atmospheric transmittance parameter acquisition in infrared radiation testing, a model for atmospheric transmittance calculation based on the HO-RF algorithm is proposed. Using key environmental factors such as temperature, humidity, operating distance, and atmospheric pressure as inputs, a regression model is established based on the measured data, enabling rapid and accurate atmospheric transmittance calculation. The simulation results show that the proposed model outperforms traditional back propagation (BP) neural network and random forest (RF) models in terms of accuracy, with a root mean square error (RMSE) reduced to 0.010745, an R² value of 0.95877, and a mean absolute error (MAE) of 0.0080021. This model effectively reduces experimental complexity and outperforms traditional methods in terms of accuracy, stability, and reliability. It can improve the efficiency of infrared characteristic testing for fighter aircraft and has excellent practical application value.

Abstract:Ground-level fine particulate matter with a diameter less than 2.5 μm (PM_2.5) has negative impacts on human health and social economy. Most methods obtain PM_2.5 data from indirect products of aerosol optical depth retrieved from satellites or daytime top-of-atmosphere reflectivity. This paper aims to directly utilize infrared data from the advanced geosynchronous radiation imager (AGRI) on the Fengyun-4B satellite and artificial intelligence models to perform near-real-time PM_2.5 retrievals over the Yangtze-Huaihe region throughout the entire day (including day and night), with a spatial resolution of 4 km and a temporal resolution of 15 minutes. Firstly, the seasonal signal response of AGRI brightness temperature to different PM_2.5 levels is explored. Secondly, a study on AGRI brightness temperature retrieval of PM_2.5 is conducted based on the random forest method in different seasons. The experimental results show that the correlation coefficients for PM_2.5 retrievals in all four seasons exceed 0.87. Finally, the model is interpretable using SHapley additive prediction (given the significant contribution of geographic information to PM_2.5), and the application of the proposed product is further explored.