Magneto-optic waveguide isolators based on laser annealed (Bi, Ga) YIG films

To overcome the effects of linear birefringence which limits the Faraday rotation achievable in magneto-optic thin film waveguides, a novel geometrical pattern of Faraday effect reversals has been designed. This pattern of P/2 segments followed by a P/4 segment where P is the birefringent period, has been built permanently into a (Bi,Ga)YIG film, with composition close to the compensation point, by laser annealing. This film provides nonreciprocal rotation of ±45° for light of wavelength 1.45 μm with an extinction ratio of 500 to 1, corresponding to 27 db of isolation.