A wide-angle dual-band infrared perfect absorber based on metal-dielectric-metal split square-ring and square array

The optical properties of a dual-band plasmonic absorber are delineated numerically by employing a finite element method. Based on a metal-dielectric-metal scheme, the key structure consists of a lossless dielectric layer that is sandwiched by a silver split square-ring enclosing a silver square array and ground silver plane. The simulation results clearly show that near-perfect absorption efficiency can be realized for two absorption bands in the near-infrared wavelength range. The near-perfect absorption bands exhibit polarization insensitivity and wide-angle incidence. Notably, the absorption band is independently governed by the size of each part of the patterned films where the silver split square-ring determines the shorter wavelength band and the silver square determines the longer wavelength band, respectively. The repositioning of two near-perfect absorption peaks possesses a linear relationship that is related to the dimensions of the patterned silver layer. This allows for a flexible reconfigurability over the entire near-infrared regime. (paper)