Tunable anisotropic absorption based on black phosphorous multilayer structures

Abstract

Black phosphorus (BP) exhibits strong anisotropy due to its specific lattice structure. In this work, we propose an absorption structure in the terahertz band, in which a two-dimensional (2D) BP metamaterial is sandwiched between dielectric layers. The proposed structure demonstrates tunable anisotropic absorption using coupling mode theory. The absorption reaches 99.4% at the resonance frequency of 8.34 THz for TM polarization, but only 17% at the same frequency for TE polarization due to impedance mismatch. The anisotropic absorption response of the structure can be attributed to the inherent anisotropy of BP and is less dependent on the incident angle. Furthermore, the light absorption can be flexibly adjusted by the Fermi level (EF) of BP, the geometrical parameters of the structure, and the refractive index of the dielectric material. These results indicate that the structure opens the way for the design of anisotropic components with the tunable spectrum and polarization selectivity.