Design of a Compact Polarization Splitter in Horizontal Multiple-Slotted Waveguide Structures

Abstract

A compact polarization splitter based on the directional coupler in horizontal multiple-slotted waveguide (HMSW) structures is proposed and designed by using a modified three-dimensional full-vectorial beam propagation method with perfectly matched layer absorbing boundary conditions. The results show that the birefringence of the HMSW is stronger than that of the single-slotted waveguide, leading to a reduction in length for the present device. Moreover, the HMSW can also enhance the optical confinement inside the slot regions. The coupling length of the directional coupler composed of two-parallel HMSWs as functions of the waveguide parameters are analyzed, and a compact device of 238.0 µm in length is achieved with the crosstalks of -27.9 and -35.6 dB for quasi-transverse-electric and quasi-transverse-magnetic modes, respectively. In addition, the evolution of the injected field along the propagation distance through the polarization splitter is also demonstrated.