One-Way Polarization Rotation by Indirect Interband Transitions

We report a theoretical demonstration of asymmetric polarized signal conversion by a sinusoidal-modulated taper polarization rotator. Based on indirect interband transition theory, periodical modulated taper introduces unidirectional conversion between quasi-TM/TE modes in a linear silicon-on-isolator system. The dependence on the sinusoidal perturbation parameters and the contribution of taper geometry are analyzed separately. The method and result presented here are expected to be valuable for the implication of on-chip isolation and optical signal processing.