Inclination of the bias magnetization in a magnetooptic waveguide yields both nonreciprocal phase shifts and polarization conversion. This enables the design of unidirectional polarization converters, i.e., waveguides that switch between orthogonal polarizations for one direction of light propagation, but keep the polarization state for light propagating in the opposite direction. Simulations of double layer raised strip waveguides show that these constraints can be met with properly adjusted geometries. The results lead to the proposal of a polarization independent integrated optical circulator based on two unidirectional polarization converters between a front and a back polarization splitter.
Manfred Lohmeyer, Norbert Bahlmann, Oleksandr Zhuromskyy, Horst tsch, and Peter Hertel, "Unidirectional Magnetooptic Polarization Converters," J. Lightwave Technol. 17, 2605- (1999)