Mode conversion and separation in magneto-optical photonic crystal waveguide.

We present mode conversion in different magneto-optical photonic crystal (MOPC) waveguides. An odd-mode waveguide (OMW) and an even-mode waveguide (EMW) are designed by adjusting the geometric parameters of the waveguide. These waveguides are constructed by adding a layer of yttrium-iron-garnet (YIG) rods with opposing magnetic fields between an MOPC and an AlO photonic crystal (PC). Due to the coupling effect caused by the middle layer of YIG rods, the OMW (or EMW) only supports an odd (or even) mode within a single-mode frequency range. Simulation results demonstrate that they can convert other modes into odd or even modes, and there is almost no power loss during the conversion. Most importantly, they are robust against backscattering from perfect electric conductors (PECs) and point defects. Based on these properties, we propose a device that can efficiently separate the odd and even modes into different ports. These results offer a novel approach to controlling the transmission modes of waveguides, which facilitates the interconnection of diverse topological magneto-optical waveguides.