Broadband magneto-optic waveguide isolator

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Abstract
Isolation ratios between −32 and −37 dB have been measured on a magneto-optic waveguide isolator over a wavelength range from 1.43 to 1.58 μm. This tunable broadband operation was achieved by rotating the input polarization angle by 22.5° from the waveguide surface of a 45° Faraday rotator to overcome the harmful effects of moderate linear birefringence. The output polarizer was then rotated to maximize the isolation ratio at each wavelength. The excess forward loss introduced by this procedure was 10% or less over this wavelength range. It is shown that excellent isolation and moderate excess forward loss (1 dB or less) can be achieved with triple garnet film, single-mode ridge waveguides over a wavelength range of ±0.2 μm around the etch-tuned wavelength, and over a temperature range of ±30 °C, which greatly enhances the usefulness of these waveguide isolators.