In this Letter, telecom-band degenerate-frequency photon pairs are generated in a specific mode of a silicon microring cavity by the nondegenerate spontaneous four-wave mixing (SFWM) process, under two continuous-wave pumps at resonance wavelength of two different cavity modes. The ratio of coincidence to accidental coincidence is up to 100 under a time bin width of 5 ns, showing their characteristics of quantum correlation. Their quantum interference in balanced and unbalanced Mach-Zehnder interferometers is investigated theoretically and experimentally, and the results show potential in quantum metrology and quantum information.

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In this paper, 1.5 μm correlated photon pairs are generated under continuous wave (CW) pumping in a silicon micro-ring cavity with a Q factor of 8.1 × 10(4). The ratio of coincidences to accidental coincidences (CAR) is up to 200 under a coincidence time bin width of 5 ns. The experiment result of single side photon count shows that the generation rate does not increase as the square of the pump level due to the nonlinear losses in the cavity which reduce the Q factor and impact the field enhancement effect in the cavity under high pump level. Theoretical analysis shows that the photon pair generation rate in the cavity is proportional to the seventh power of the Q factor, which agrees well with the experiment result. It provides a way to analyze the performance of CW pumping correlated photon pair generation in silicon micro-ring cavities under high pump levels.

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.