An Efficient Technique for Evaluating the Characteristics of a Polarization Converter Consisting of an Asymmetric Waveguide

An efficient and accurate technique for evaluating the characteristics of a polarization converter consisting of a dielectric waveguide with a single asymmetric section is proposed and discussed with the aid of the imaginary-distance beam-propagation method. Detailed consideration regarding the optical-axis rotation angle reveals the necessity and effectiveness of introducing the excitation efficiency of the two hybrid eigenmodes of the asymmetric section. This enables us to assess the incident mode dependence, which cannot be done by the conventional rotation angle. We derive concise formulas regarding the polarization extinction ratio and the insertion loss using the hybrid eigenmodes. It is found that the present formulas provide reasonable results, showing a good agreement with the results obtained from a time-consuming FDTD simulation.