Magneto-optic buried channel waveguides for a 45° nonreciprocal waveguide rotator

An optical isolation ratio of −21.1 dB at λ=1.55 μm is obtained for a LPE-grown La and Ga substituted YIG single-mode buried channel waveguide. Waveguides about 3 mm long end-butted to single-mode fibers show an overall insertion loss of less than 2 dB. The Ar ion-beam etching technique using a three layered etching mask provides sufficient control of both the width (∼4 μm) and height (∼4 μm) of the core ridge. The core and cladding layers are individually grown from melts with different compositions in order to reduce stress-induced birefringence. The good reproducibility with which 45° waveguide rotators exhibiting a circular near-field intensity pattern can be fabricated will enable us to realize optical integration in future systems.