Fabry–Pérot resonance cavity enabling highly polarization-sensitive long-wave infrared detector via double-layer linear grating

Au gratings are widely employed as the primary architecture in infrared linear polarization detectors; however, they suffer from significant optical losses in the long-wave infrared range, resulting in limited extinction ratios. In this study, we present a highly polarization-sensitive Au/SiO₂ double-layer linear grating integrated into InAs/GaSb superlattice-based long-wave infrared detectors. Finite-difference time-domain simulations demonstrate that by leveraging the Fabry–Pérot resonance cavity within the SiO₂ grating, the structure enhances the transmittance of TM-polarized light while suppressing that of TE-polarized light, thereby significantly improving the extinction ratio. Compared to conventional Au grating-based polarization detectors, the proposed device exhibits superior responsivity to TM-polarized light and a higher extinction ratio across the 8–14 μm wavelength range. Specifically, the extinction ratio improves by a factor of 1.25 at 9.2 μm. This approach offers an effective strategy for advancing high-performance long-wave infrared linear polarization detectors.