Yttrium iron garnet single-mode buried channel waveguides for waveguide isolators

Magneto-optic single-mode buried channel waveguides in substituted yttrium iron garnet suitable for waveguide isolators have been prepared. The channels are fabricated in a three-step procedure: starting with multiple-layer planar single-mode waveguides, rib waveguides are wet etched and then overgrown with top cladding. Such waveguides show mode profiles well matched to that of single mode fibers. In mode conversion experiments, an extinction ratio of 20 dB was obtained. Waveguides coupled to single-mode fibers on both sides showed an overall insertion loss of about 4 dB.