Polarization-selective dual-band infrared plasmonic absorber based on sub-wavelength gaps

A dual-band (mid- and long-wave infrared) polarization-selective plasmonic absorber was designed and numerically investigated. This absorber traps definite polarization light and reflects light that is perpendicular to the polarization direction. It is extremely sensitive to polarization angle and can keep robustness to oblique incidence. The extinction rate does not reduce when the incident angle is even near 80°and rate value keeps above 130 for both resonance peaks. The absorber can respond to mid- and long-wave infrared atmospheric windows simultaneously and achieve near-unity absorption at 3.3 μ m and 9.8 μ m for specific polarization under normal radiation. The resonance condition is tuned by altering the geometric design. Owing to its high absorptivity and fine polarization properties, the absorber combines the advantages of a light absorber and a polarizer, and can be utilized in an uncooled infrared polarization detector, which simplify the optical system design and avoid the polarization information reconstruction error caused by the misplacement between the polarizer and the pixel.