Polarization-entangled sources using waveguide-coupled two-microring-resonators in a silicon nitride platform

We demonstrate polarization-entangled photon-pairs in a Si3N4 platform adopting a single-waveguide-coupled two-microring-resonators structure. We design different microring parameters to obtain indistinguishable orthogonally polarized photon-pairs in the spectral domain. The measured visibility is ~ 85%.