Design of high isolation ratio optical isolators based on magneto-optical plasmonic waveguides

In this paper, ultra-compact, high isolation-ratio optical isolators for use in wavelength-division multiplexing networks are presented. The isolator is composed of two parts, including a straight waveguide and a resonator. The performance of the isolator is investigated for two kinds of disk and ring resonators. The structure is based on the metal-insulator-metal configuration in which the metal parts are of gold and the insulator parts are of a magneto-optical material. The effecting parameters, including the dimensions of the disk/ring resonator, the gap between the waveguide and the resonator, and the waveguide material are comprehensively studied using the finite-difference time-domain method. By changing the geometrical variables and materials, the isolation ratio of the disk-and ring-based isolators can reach up to 33.47 dB and 29.06 dB, respectively. The footprint of both isolators is less than 1 mu m2. The proposed isolators can be used in photonic integrated circuits due to their ultra-compact footprint, high isolation ratio, and CMOS-compatible structures.