FARADAY ROTATOR FOR AN OPTICAL DEVICE

摘要

A Faraday rotator comprises a ferrimagnetic garnet film epitaxially grown on a non-magnetic garnet substrate and a magnet for inducing a magnetic field in the film to rotate the plane of polarization of a light beam applied to the film. The substrate and the film are made of a material such that the absolute value of the difference between the lattice constant of the substrate and that of the film is less than or equal to 0.001 angstrom units. This low value of mismatch has the effect of obtaining isolation of at least 25 dB in the rotator. Techniques for reducing surface roughness and inappropriate light incidence to the filling two further causes of poor isolation properties, are also described.