Silicon waveguide optical nonreciprocal devices based on magneto-optical phase shift

Abstract

The nonreciprocal phase shift caused by the first-order magneto-optical effect is effective in realizing optical nonreciprocal devices such as optical isolators and circulators in silicon waveguide platforms. The low refractive index of the buried oxide layer in a Silicon-On-Insulator (SOI) waveguide enhances the magneto-optical phase shift, which reduces the device footprints. In order to obtain the magneto-optical phase shift, it is required to integrate a magnetooptical material on the silicon waveguide. A surface activated direct bonding technique was developed to integrate a magneto-optical garnet single crystal on the silicon waveguides. Using this technique, a silicon waveguide optical isolator based on the magneto-optical phase shift was demonstrated with an optical isolation of 30 dB at a wavelength of 1548 nm. Furthermore, a four port optical circulator was demonstrated with maximum isolations of 33.5 and 29.1 dB in cross and bar ports, respectively, at a wavelength of 1543 nm. Excess insertion losses were 13 and 12.5 dB in the isolator and circulator, respectively.