Robust one-way modes in gyromagnetic photonic crystal waveguides with different interfaces

We experimentally realize a one-way waveguide made from a gyromagnetic photonic crystal (GPC) and a normal dielectric photonic crystal in their common photonic band gap. Due to the time reversal symmetry breaking of the GPC under a dc magnetic field, the edge modes exhibit a one-way property. We investigate the unidirectional propagation character originating from the chiral edge states at different widths of the waveguide. Both the forward modes, which are robust to various obstacles, and the backward modes show an obvious frequency shift for different waveguide widths. Numerical simulations by means of the transfer-matrix method and multiple scattering methods agree well with the experimental data.