Design of a compact polarization splitter composed of multiple-slotted waveguide and silicon nanowire

摘要

A polarization splitter (PS) based on a directional coupler (DC) composed of vertical multiple-slotted waveguide (MSW) and silicon nanowire is proposed and designed by using a modified three-dimensional full-vectorial beam propagation method (BPM). By utilizing the unique modal properties of the slot waveguide, the coupling of the DC in quasi-TE modes can be almost neglected, and only that in quasi-TM is considered, leading to a compact PS. Moreover, the MSW has the advantages of both strong field confinement and high birefringence, which improves the performance of the present device. The numerical results show that a PS with a length of 20.5μm in the coupling region is achieved whose bandwidth is up to 22nm (ranged from 1.540 to 1.562μm) with the crosstalk lower than -20dB. In addition, the fabrication tolerances to the structural parameters are investigated in detail. And the evolution of the injected field along the propagation distance through the PS is also demonstrated.