Abstract:An improved mercury-rich vertical liquid-phase epitaxy (LPE) technique is described. This technique achieves the growth of HgCdTe materials through the optimization of graphite boat design and the control of growth solution. By optimizing the temperature field with flow field simulation calculations, the material quality is significantly improved. The material′s thickness standard deviation is less than 0.23, and its composition standard deviation is less than 0.001. This technique successfully achieved the growth of multiple 36 mm×42 mm HgCdTe bilayer heterojunction materials in a single operation, with stable mass production. The obtained material meets the requirements for the development of large-array p-on-n infrared focal plane detectors in terms of key performance indicators such as thickness uniformity, doping concentration, and surface defects.

Abstract:Photoconductive antenna (PCA) is one of the most commonly used terahertz (THz) radiation sources in terahertz time-domain spectroscopy systems. Based on the principle of terahertz signal generation by PCA, a fiber-coupled terahertz radiation source module excited by a 1560 nm laser is designed and simulated using a PCA chip based on InGaAs/InAlAs superlattice. Through the integrated design of optical path and structure, a miniaturized fiber-coupled terahertz radiation source is achieved. Under excitation with a femtosecond pulse laser with an average power of 25 mW, a pulse width of 100 fs, and a central wavelength of 1560 nm, the terahertz signal spectrum obtained from a single waveform sampling of the terahertz radiation source extends from 0.1 to 2.9 THz, with a dynamic range of 57 dB. Furthermore, the relationship between the output signal amplitude of the terahertz radiation source and the bias voltage and excitation light power is experimentally investigated.

Abstract:Ultrashort terahertz (THz) pulses coupled with the scanning tunneling microscopy possess imaging capabilities with ultra-high spatial-temporal resolution, offering promising applications in material surface imaging, property diagnosis, and testing. The operating principle of THz tunneling scanning microscopy and the factors influencing the tunneling current are analyzed based on the Simmons model. Combined with numerical calculations, the influences of THz pulse parameters and sample work function on the barrier and tunneling current are studied in detail. The results show that the tunneling current is a periodic function of the THz pulse phase. The tunneling current induced by the THz electric field and the DC bias electric field has a critical value, determined by the work function of the material. Above this critical value, the tunneling current becomes a linear function of the THz electric field. As the THz pulse width increases, the number of electrons rectified by the tunneling current decreases in an oscillatory manner and tends to be stable. These research results have a good reference value for an in-depth understanding of the microscopic physical mechanism of terahertz tunneling scanning microscopy technology and guiding related experiments.

Abstract:To better characterize the radiation polarization characteristics of the object surface, a two-component polarization bidirectional reflectance distribution function (PBRDF) model based on the Cauchy distribution is established based on the P-G model and the distribution of microfacets on the surface. Based on the transmission characteristics of infrared polarization radiation, a linear polarization model for infrared radiation is derived using the blackbody radiation law. This model is then tested through a designed infrared polarization imaging experiment. Measured data are compared with numerical calculation results to analyze the impact of the Cauchy distribution on the accuracy of the infrared polarization model compared to the Gaussian distribution. The results show that the micro-facet model characterized by the Cauchy distribution is more suitable for describing the infrared polarization degree of an object surface. These findings provide theoretical and technical support for further optimizing the accuracy of the bidirectional reflectance distribution function (BRDF) model.

Abstract:As a non-contact temperature measurement tool, infrared thermal imagers offer significant advantages in hot stamping processes. However, their measurement accuracy is susceptible to multiple factors, including surface emissivity, observation angle, and target temperature. A temperature measurement optimization method based on dynamic emissivity compensation is proposed. Projection measurement technology is used to accurately obtain the spatial angular parameters of complex curved parts. Then, the effect of observation angle and temperature value on temperature measurement deviation is quantitatively analyzed through experiments. A machine learning algorithm is employed to construct a nonlinear mapping model between emissivity and multidimensional variables, enabling intelligent compensation of dynamic emissivity parameters. Experimental results show that after compensation, the temperature measurement system error can be stably controlled within the range of ±1.5 °C, improving accuracy by 60% compared to the fixed emissivity mode. This method provides an effective solution for the application of high-precision infrared temperature measurement in intelligent manufacturing scenarios.

Abstract:Accurately locating the boundary points of complex-shaped tunnel contour changes and extracting the contours of each segment can provide strong support for tunnel deformation monitoring, point cloud orthophoto generation, and reconstruction of existing tunnel models. Based on high-precision tunnel point cloud data collected by mobile laser scanning, the original cross-section point cloud is first extracted and preprocessed, and then contour changes are identified by using the neighborhood density features of contour feature points. Finally, the mileage positioning method and boundary extraction algorithm are combined to complete the tunnel segmentation and contour extraction. Experiments using measured data from a subway tunnel and a highway tunnel verify the feasibility of this method. Compared with existing research, this method breaks away from the high dependence on the tunnel′s central axis, can independently and accurately identify contour changes, and effectively improves processing efficiency. It provides an efficient and innovative solution for engineering applications related to complex-shaped tunnel segmentation and contour extraction, and has a certain reference value for the application optimization of high-performance laser scanning technology.