Etch-tuned Ridged Waveguide Magneto-optic Isolator.

Isolation ratios as large -33 dB at wavelengths near 1.5microns have been measured on ridged waveguide Faraday rotation isolators. Single mode, triple layer bismuth-yttrium iron garnet films were chemically etched to reduce the linear birefringence of the active top layer to zero. Ion-implantation enhanced etching was used to create ridges 8microns wide and 0.5microns high. Using fiber coupled light from a tunable color center laser, isolation ratios of -20 dB or better were achieved over a wavelength range of +/-0.05microns near 1.5microns.