Polarization and sizes variation immune optical absorbers
Abstract
In this paper, a novel optical absorber that is flexible in size for fabrication and unique properties is studied numerically by aid of finite difference in time domain (FDTD) algorithm. The structure consists of three layers based on the metal–dielectric–metal design scheme. The middle layer is a dielectric in which the electronic and magnetic resonance energy dissipates. The bottom side is a metallic plane and the top layer is a hexagonal prism array. We also investigate the influence of the structure parameters on the absorbance and the absorption wavelength. The results show that a perfect absorber can be designed, and the number of the absorption peaks varies from two to three for the different radius of circumcircle of the hexagonal prism ranging from 280 nm to 400 nm. Meanwhile, position of the first absorption peak is nearly unchanged. This unique feature may be a significant advantage and possesses great potential applications such as biosensing and photovoltaic. Additionally, position and amplitude of the first absorption peak is constant for broad incident angles. The absorption is insensitive to the polarization of the incident beam due to the highly symmetric structure.
