A TM polarization absorber based on a graphene–silver asymmetrical grating structure for near-infrared frequencies

Abstract

In this paper, a TM polarization multi-band absorber is achieved in a graphene–Ag asymmetrical grating structure. The proposed absorber can achieve perfect absorption at 1108 nm, 1254 nm, and 1712 nm (the absorption exceeds 98.4% at the three peaks). Results show that the perfect absorption effect originates from the excitation of magnetic polaritons (MPs) in the silver ridge grating; a LC equivalent circuit model is utilized to confirm the finite-difference-time-domain (FDTD) simulation. The influences of the incident angle, polarization angle, and geometrical size on the absorption spectrum are investigated. Moreover, a quadruple band absorber and a quintuple band absorber are also designed by introducing more silver grating ridges in one period. The proposed graphene–Ag asymmetrical structure has some advantages compared with other absorbers such as the ability to be independently tuned and a simple structure. Thus, the proposed structure can be applied in the areas of multiple absorption switches, near-infrared modulators, and sensors.