Strong optical non-reciprocity in one-dimensional photonic crystal containing a Weyl semimetal-based defect

Abstract

Optical non-reciprocity possesses a broad range of applications in the design of optical diodes, insulators, circulators, and logical devices. A conventional method to realize optical non-reciprocity is to break the Lorentz reciprocity by introducing magneto-optical materials. However, the realization of strong optical non-reciprocity based on magneto-optical materials usually requires strong external magnetic field, which poses a challenge to observe strong optical non-reciprocity in experiments. Recently, a kind of bulk topological materials called Weyl semimetals attracted researchers’ great interest since they possess the intrinsic Lorentz non-reciprocity. In this paper, we introduce a Weyl semimetals-based layer as a defect into a one-dimensional photonic crystal to achieve strong optical non-reciprocity without applying an external magnetic field. A theoretical model based on the transfer matrix method is proposed to calculate the transmittance for the forward and backward incidences of the structure. By optimizing the parameters, the wavelength difference between two defect modes for the forward and backward incidences in the proposed structure reaches 107 nm, which is two orders higher than that in a one-dimensional photonic crystal containing a InSb-based defect under a 1 T external magnetic field. This strong optical non-reciprocity in simple 1D structure would possess applications in the design of compact passive non-reciprocal devices. By introducing a Weyl semimetal-based defect layer into the one-dimensional photonic crystal, strong optical non-reciprocity at mid-infrared wavelengths can be achieved. The wavelength difference of the defect modes between the forward and backward incidences reaches 107 nm. • A Weyl semimetal (WSM)-based defect layer is introduced into a one-dimensional photonic crystal (1DPC). • Strong optical non-reciprocity at mid-infrared wavelengths is achieved in the 1DPC containing a WSM-based defect layer. • The wavelength difference of the defect modes between the forward and backward incidences reaches 107 nm.