Polarization-sensitive metamaterial absorber based on the composite grating structure in the long-wave infrared band

Infrared absorbers exhibiting polarization-sensitive performance are in great demand in numerous applications, including imaging, sensing, and detection. Here, A novel polarization-sensitive absorber (PSA) based on the composite grating structure is proposed in the long-wave infrared band (LWIR). Based on gap resonance, localized surface plasmon (LSP), and Fabry–Pérot (F-P) resonance modes, the proposed absorber has two absorption peaks (12.04 μm and 13.14 μm) in TM mode and a single absorption peak (8.76 μm) in TE mode. On this basis, a coupling resonant state of Gap resonance and LSP resonance is added to the TM polarization mode. The optimized absorber achieves the broadband absorber characteristics in TM mode, and the average absorption rate reaches 85.3 % in the range of 6–14 μm and even 91.2 % in the range of 7–13 μm. The substrate metal grating is the main absorption loss component in both TE and TM modes. Two different absorption modes are achieved by switching the polarization state of incident light (TM/TE). It can be used for polarization detection, improves the applicability of infrared equipment to complex environments, and is crucial for developing infrared equipment.