Nonreciprocal light channeling in a film by a magnetic nonuniformity akin to a Neel domain wall

Abstract

The problem of light propagation along a magneto-optic nonuniformity which is similar to a wide Neel domain wall is analyzed by perturbation theory. The Maxwell equations of the three-dimensional problem are reduced to a system which describes the amplitude evolution of the coupled TM and TE modes in a two-dimensional approximation. Numerical analysis shows a strong nonreciprocal character of light beam propagation: The waveguide supports a localized TRI-like mode in one direction and scatters the light beam in the opposite direction. For a garnet film of 1 mu m thickness, having a Faraday rotation of 3150 degrees/cm at a wavelength of 1.3 mu m, an isolation of 25 dB is calculated for a propagation length of 1 cm. This waveguide may be used as optical isolator. It may also be applied as a magneto-optical switch or modulator tuned by an external magnetic field. (C) 1998 American Institute of Physics.