Design and Simulation of Silicon Waveguide Optical Circulator Employing Nonreciprocal Phase Shift

In this paper, we propose an optical circulator employing a nonreciprocal phase shift with a silicon waveguide. Two types of optical circulators are investigated, a perfectly circulating four-port optical circulator and a three-port optical circulator. Nonreciprocal characteristics are obtained owing to the first-order magneto-optic effect of a magneto-optic garnet directly bonded onto a silicon guiding layer. The waveguide structure is designed by numerical simulations. When we use a 220-nm-thick and 500-nm-wide silicon waveguide core, the required length of the nonreciprocal phase shifter is 348.3 µm at a wavelength of 1.55 µm. The four-port optical circulator exhibits a crosstalk below -20 dB in a wavelength range between 1.54 and 1.56 µm. The three-port optical circulator exhibits a crosstalk below -20 dB in a wavelength range between 1.53 and 1.57 µm. The total length of both types of optical circulators is approximately 420 µm.