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 μm². The proposed isolators can be used in photonic integrated circuits due to their ultra-compact footprint, high isolation ratio, and CMOS-compatible structures.