Enhancing the Faraday rotation of monolayer black phosphorus by the optical Tamm state at the photonic crystal interface.

Abstract

Black phosphorus (BP) is a two-dimensional material with a direct bandgap that exhibits in-plane anisotropy, high charge carrier mobility, and excellent optical properties. It also can demonstrate a strong magneto-optical response under an external magnetic field. In this paper, we present a theoretical study to enhance the Faraday rotation of the monolayer BP by the optical Tamm state at the interface between two photonic crystals. The optical Tamm state can increase the Faraday rotation angle significantly through the localization of the electromagnetic field with high transmittance. When the externally applied magnetic field is 5 T, the gain in the Faraday rotation angle can reach 37.37 dB with a transmittance greater than 65%. The Faraday rotation angle can be adjusted proportionally by the external magnetic field while retaining the high transmittance, and the operating frequency also remains unchanged. In addition, the Faraday rotation angle and operating frequency can be adjusted by changing the carrier density and photonic crystal parameters.