Low temperature O2 plasma-assisted wafer bonding of InP and a garnet crystal for an optical waveguide isolator

Abstract

A novel process of wafer bonding between InP and a garnet crystal (Gd 3Ga5O12, CeY2Fe5O 12) based on O2 plasma surface-activation and low temperature heat treatment is presented. The O2 plasma assisted wafer bonding process was found to be very effective in bonding of InP and Gd 3Ga5O12, providing good bonding strength and hydrophilicity as well as no voids in the interface, which is crucial for fabrication of an integrated optical waveguide isolator. The isolation ratio of an integrated optical waveguide isolator fabricated by the O2 plasma assisted wafer bonding process was obtained to be 2.9 dB.