Demonstration of a Silicon Waveguide Optical Circulator

A four-port optical circulator based on a Mach-Zehnder interferometer is fabricated in a silicon nanowire waveguide. A magneto-optical garnet is directly bonded to the silicon waveguide using a surface activated bonding technique. Four-port circulator operation is demonstrated with a maximum isolation of 15.3 dB at a wavelength of 1531 nm.