Silicon-based Magneto-optical Isolator and Circulator Fabricated by Direct Bonding Technology

We have investigated magneto-optical isolator and circulator on silicon photonics circuits using a direct bonding of silicon and a magneto-optic garnet. The devices are based on a Mach-Zehnder interferometer (MZI) composed of Si waveguides. Bonded magnet-optic garnet as an upper cladding layer induces nonreciprocal phase shift in a push-pull manner by applying magnetic fields in the Voigt configuration. Depending on the number of input and output ports, an MZI becomes an isolator or a circulator. In our recent development, an optical isolator with 30 dB isolation and a 4-port circulator are demonstrated.