Research on mid-wave infrared band-stop filter based on metal metasurface

A filter based on metasurface structure exhibits advantages such as thin thickness and ease of integration, significantly reducing the volume and weight of infrared detection and laser beam control systems. In this paper, we design a metasurface-based band-stop filter operating in the mid-infrared band (3-5 μm). Sapphire is chosen as the substrate material for the filter. Above the antireflective layer, cross-shaped meta-atoms composed of aluminum are arranged. By optimizing the geometric parameters and layout of these meta-atoms, simultaneous band-stop filtering at nine distinct wavelengths can be achieved. Metallic isolation layers were incorporated between adjacent unit cells to suppress the electromagnetic coupling between adjacent unit cells. Full-wave electromagnetic simulations (FDTD) of the metasurface demonstrate that the stopband transmittance is below 35% and the central wavelength deviation is less than 25 nm (0.1wavelength). And the central wavelength deviation is below 25 nm. The optical performance of this band-stop filter satisfies the spectral requirements for optical imaging instruments, enhancing the accuracy of infrared sensing and detection.