▎ 摘　　要

In this work, we theoretically investigate non-reciprocal propagation of terahertz (THz) waves through a photonic crystal cavity integrated with graphene under external magnetic field. The magnetic field applied perpendicular to the graphene plane introduces an asymmetric conductivity tensor into the system, thus the Jones matrix of THz waves propagating in one direction is not the transpose of the one in the reversal direction. As a consequence, non-reciprocal propagation is achieved in the THz regime, which has been verified by the calculation of nonreciprocal photonic band structures, transmission spectra, and also electrical-field distributions. Further, by tuning the magnetic field or the Fermi level of graphene, such non-reciprocal transmission can be drastically tuned. This tunable non-reciprocity at the level of material response enables us to design photonic structures which can let a specific mode pass but its time-reversal counterpart stop. Moreover, high-performance non-reciprocal features have been found in periodic photonic crystal stacks with graphene. Our investigations may provide a unique approach to guide THz waves and achieve potential applications on one-way devices (e. g. isolators) in the THz regime. Copyright (C) EPLA, 2014