Nonlinear optics of gyrotropic media: second harmonic generation in rare-earth iron garnets

Second harmonic generation in nonlinear gyrotropic media in the form of epitaxial films of rare-earth iron garnets was investigated for the first time both experimentally and theoretically. The anisotropy of the process in a magnetic field, as well as the Faraday and Kerr effects were studied. In the nonlinear interaction case the Faraday effect was half that in the linear case. An expression was obtained for describing the Faraday and Kerr effects for the case of a nonlinear interaction involving a semiinfinite nonlinear gyrotropic medium and a nonlinear gyrotropic layer: a characteristic feature of these effects was a nonlinear coordinate dependence. The experimentally observed characteristics of the two effects were explained by a model allowing solely for the linear magnetooptic parameters of the medium. Possible mechanisms of the appearance of the nonlinearity in iron garnets in a magnetic field were analyzed.