Ultrahigh extinction ratio and ultralow insertion loss for polarization beam splitter based on two folded asymmetrical directional couplers with dual-stage etching.

Abstract

We propose and experimentally demonstrate a polarization beam splitter (PBS) with excellent performance in terms of ultrahigh extinction ratio and ultralow insertion loss. The PBS consists of two dual-stage etched asymmetrical directional couplers, which are cascaded by a bend waveguide to form a folded structure. In the PBS, the fundamental transverse magnetic (T M 0) mode is efficiently cross-coupled to the cross-port, while the fundamental transverse electric (T E 0) mode outputs at the through-port. Thanks to the cascaded structure and dual-stage etching, a silicon-on-insulator-based PBS with ultrahigh extinction ratio and ultralow insertion loss is achieved. The measurement results reveal an extinction ratio beyond 25dB and an insertion loss less than 0.7dB within a wide bandwidth of 175nm for the T E 0 and T M 0 modes.