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Real-time polarization medium-wave infrared (MIR) optical imaging systems enable the acquisition of infrared and polarization information of a target. At present, real-time polarization middle-infrared devices mainly face the following problems: poor real-time performance, low transmission, and high requirements for fabrication and integration. Herein, we need to improve the performance of the real-time polarization imaging system in the MIR waveband and solve the above-mentioned defects. Therefore, we propose an MIR polarization imaging system for achieving real-time polarization-modulated imaging with high transmission as well as improved performance based on a pixel-wise metasurface micro-polarization array (PMMPA). The PMMPA element comprises several linear polarization (LP) filters with different polarization angles. The optimization results demonstrate that the transmittance of the LP filters is up to 77% at a wavelength of 4.0 μm and an extinction ratio of 88 dB. In addition, a near-diffraction-limited real-time MIR imaging optical system is designed with a field of view (FOV) of 5ºand an F-number of 2. The simulation results show that an MIR polarization imaging system with excellent real-time performance and high transmission is achieved by using an optimized PMMPA element. Therefore, the method is compatible with the available optical system design technologies and provides a way to realize real-time polarization imaging in mid-infrared wavebands.

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The wettability mechanism of soil-water interfaces is of significant importance in geotechnical engineering. However, the effect of different contact angles on unsaturated sand soil behavior has been less understood. In this study, the wetting behavior of nano water droplets on various silica substrates is investigated using molecular dynamics. Seventeen groups of simulation systems with different interaction potential energies (ε Si = 0.008, 0.04, 0.2, 0.4, 0.6, 0.8, 1, 2 kcal/mol) and temperatures (T = 273, 298, 323, 353 K) are conducted. The results show that the contact angles varies intensively with interaction potential energies from 108.5°to 18.1°, which indicates a transition from hydrophobic to hydrophilic and wettability enhancement along with the increase of interaction potential energy. Simulation results also show that contact angles increase with the increase of temperature, whatever the hydrophobic or hydrophilic of the silica surface. Such phenomena are interpreted from the perspective of microstructure, along with the performance of macrostructure. In addition, results show that the contact angles are independent of the thickness and width (length) of silica substrate.