15 μm polarization entanglement generation based on birefringence in silicon wire waveguides

In this Letter, the 1.5 μm polarization entanglement generation is realized in a silicon wire waveguide utilizing its birefringence. In this scheme, two orthogonal polarized correlated states are generated by scalar processes of spontaneous four-wave mixing (SFWM) in the quasi-transverse electrical and quasi-transverse magnetic modes, respectively. Meanwhile, the vector processes of SFWM are suppressed by the group birefringence in the waveguide. The maximum polarization entangled state is generated by optimizing the pump polarization, which is demonstrated by the experiments of two-photon interference and polarization indistinguishability at one side. The fringe visibilities of two-photon interferences are 96.8±4.7% and 86.0±3.7% under two nonorthogonal polarization detection settings, respectively. This scheme provides a simple way to realize silicon integrated sources for 1.5 μm polarization entanglement generation.