Waveguide optical isolators fabricated by wafer bonding

Wafer bonding of a magnetooptic garnet crystal to III-V compound semiconductor and LiNbO₃ is discussed for the application to waveguide optical isolators. Two types of waveguide isolators, an interferometric isolator and a semileaky isolator, are discussed. The interferometric isolator uses nonreciprocal phase shift and is composed of the GaInAsP guiding layer. The isolator has the advantage of integratability with optical active devices. The semileaky isolator composed of a magnetooptic garnet guiding and LiNbO₃ upper cladding layer has the advantages of large fabrication tolerance and wide operating wavelength range. The performance of isolators is also demonstrated.