Terahertz and Mid-and Long-wave infrared high-efficiency beam splitting devices based on metasurfaces

Abstract

The multi-mode composite imaging technology combines the advantages of different sensors, and has the advantages of high image quality, strong information acquisition ability, high target detection and recognition ability, strong adaptability to complex environments, and high stability and robustness of the system. Among them, the terahertz and infrared composite imaging technology combines the characteristics of terahertz band and infrared band, has the advantages of wide spectrum coverage, high resolution and strong penetration, and has broad application prospects. As one of the key components of the common aperture composite imaging system, the high efficiency optical splitters in terahertz and infrared band are still lacking at present, and their performance needs to be improved urgently.<br>In this paper, a kind of dichroic metasurface with a simple structure and high performance is proposed by combining simulation experiment and theoretical explanation. When used as a spectral device, when the incident Angle is 45°, it achieves a transmission coefficient greater than 97% near the center frequency of 1.1 THz, and a reflection coefficient greater than 98% in the wavelength range of 3-5 μm in medium-wave infrared and 8-14 μm in long-wave infrared. The design has good robustness to structural mismatches and machining errors such as structural misalignment, structural fillet, small magnification scaling, and polarization insensitivity. When the incidence Angle changes in the range of 0-60°, the device still maintains excellent spectral characteristics. In this paper, based on Babinet theorem and equivalent circuit model, the electromagnetic response characteristics of the metasurface are analyzed theoretically, and the analysis results are in agreement with the simulation results. The results of this study prove the feasibility of metasurface as a spectral device in the multiwavelength composite imaging system of terahertz and infrared bands, and provide support for the future research of new composite imaging detection technology. In addition, the metasurface structure in this paper has a strong application prospect in many fields, such as multi-band infrared stealth, laser and pump light separation in lasers, and provides a valuable design reference for terahertz and infrared spectroscopy in various scenarios.