Tunable and robust reflection-free waveguides based on a gyromagnetic photonic crystal

We propose and numerically investigate a kind of tunable and robust reflection-free waveguides based on a gyromagnetic photonic crystal (PC). The time reversal symmetry breaking of the gyromagnetic PC under out-of-plane dc magnetic fields gives rise to one-way edge modes in both the second and third band gaps. It is found that the propagating properties of one-way modes in the waveguides can be easily controlled by adjusting the directions of external magnetic fields. Moreover, the one-way modes are robust against the disorder in the waveguides.