Studies Of One-way Electromagnetic Edge Mode

Photonic one-way edge mode and related nonreciprocal devices based on magneto-optical (MO) photonic crystals (PhCs) is a emerging research direction in the field of PhCs. In the case with an external dc magnetic field applied onto the MOPhCs, strong gyroelectric or gyromagnetic anisotropy can be induced in the MOPhCs, which breaks the time-reversal symmetry of the PhCs, and then surface mode that propagates in only one-way direction could be supported at the edge of MOPhCs. This paper will further investigate the physical properties of one-way electromagnetic edge mode of PhCs on the basis of previous studies. Up to now, studies have focused mostly on the PhC structures of dielectric rods in air, and their complementary structures have received less attention, which are PhCs formed by arrays of air columns in the dielectric background. The latter type allows more flexibility in PhC boundary cutting. In this thesis, we consider yttrium-iron-garnet (YIG) two-dimensional PhCs formed by a triangular lattice of air columns in YIG, and investigate relationship between the boundary shape of a truncated YIG PhC and sustained edge modes. Our studies show that the interface between a YIG PhC and air may support unidirectional or bidirectional propagating edge modes, or even no mode, closely depending on the boundary shape of the truncated PhCs. In addition, surface wave transmission along the edge of the YIG gyromagnetic PhCs is numerically simulated at microwave frequencies, which verifies the physical phenomena of the unidirectional edge mode. Finally, this paper also presents a design of gyroelectric PhC structure with indium antimonide (InSb) dielectric which supports one-way edge mode operating at terahertz frequencies, and the characteristics of terahertz one-way edge mode are carefully analyzed.