Multiband Perfect Absorption Induced by Fundamental Magnetic Polaritons

In this paper, a new structure of directional insensitive multiband perfect absorption was proposed, which combined the optical phonon material and the nondispersive dielectric material as the spacer layer of a single sized Metal/Dielectric/Metal micro grating. Multiband absorption induced by magnetic polariton was excited at atmosphere window wavelength band. The spectral absorptivity and electromagnetic field distribution were calculated via finite element method. Effects of incident angle and geometric parameters on absorption were also investigated. Considering that the nature of magnetic polaritons is the reverse current oscillation induced by the lower surface of the metal grating and the upper surface of the metal substrate, the multilayer film functions as a dielectric spacer. Effective medium theory (EMT) approximation treatment of multilayer film was performed. LC circuit model with EMT treatment to predict the magnetic polariton resonance condition was verified hereafter. The multiband absorption mechanism proposed in this paper has a bright future in infrared detection, radiative cooling and other fields.