An integrated optical waveguide isolator based on multimode interference by wafer direct bonding

An integrated waveguide optical isolator based on multimode interference (MMI) by wafer direct bonding has been studied. It was found that wafer direct bonding between InP and Gd/sub 3/Ga/sub 5/O/sub 12/ (GGG) is effective for the integration of a waveguide optical isolator. The isolation ratio was found to be 2.9 dB in the proposed device.