Design of ultra-low insertion loss active transverse electric-pass polarizer based Ge2Sb2Te5 on silicon waveguide

An active transverse electric (TE) pass polarizer with ultra-low insertion loss (IL) is proposed based on asymmetrical directional coupler consisting of a silicon waveguide and a silicon hybrid waveguide with phase change material of Ge2Sb2Te5 (GST). The tunability of the polarizers relies on the considerable change of the optical properties of the GST between the amorphous and crystalline phases. We numerically demonstrate a 5.5-μm-long active polarizer has an ultra-high IL of above 28 dB for the unwanted transverse magnetic (TM) mode and the ultra-low IL of as little as 0.12 dB for TE mode with the crystalline phase of GST. When trigger to the amorphous phase, the device nearly exhibits transparent with the negligible IL for TE/TM mode. The proposed device possesses a broadband of ∼200 nm with a high extinction ratio (ER) as well as relative large fabrication tolerance.