  We propose and demonstrate a hybrid waveguide platform using layered
amorphous silicon and silicon nitride. The waveguide offers more degrees of
freedom to design waveguides with desired confinement, effective index and
polarization birefringence. Unlike single core material, the proposed waveguide
offers design flexibility, and light confinement in the layers is
polarization-dependent. We present a detailed waveguide design and analysis of
efficient fiber-chip grating couplers with a coupling efficiency of -3.27 dB
and -8 dB for $TE$ and $TM$ polarization, respectively. The couplers offer a
3dB bandwidth of 100 nm. Furthermore, we demonstrate excitation of TE and TM
modes exploiting the polarization-dependent confinement using thermo-optic
characteristics of a ring resonator.
