Study of asymmetric silicon cross-slot waveguides for polarization diversity schemes

We study cross-slot waveguides for polarization diversity schemes that simultaneously offer strong confinement in the slot region for both TE and TM polarizations. A symmetric configuration is initially presented to demonstrate that the same strong confinement and propagation constants can be obtained for both polarizations and slot thicknesses down to 50 nm. To make easier further realization of these waveguides, an asymmetric waveguide configuration with a vertical slot height of up to 120 nm is proposed. The waveguide parameters are then optimized taking into account a 220 nm silicon thickness. Our simulation results show that no beating issues between TE and TM modes is observed for beating lengths under 6.68 microm, thus opening the way to efficient implementations of polarization diversity approaches.