Microcavities with high Q factor and small mode volume have the potential to be efficient and compact sources of photon pairs. Here, we demonstrate on-chip photonpair generation by spontaneous four-wave mixing in a silica microtoroidal cavity and obtain a coincidence-to-accidental ratio of 7.4±0.1 with a pump power of 46 μW. The heralded photons also exhibit antibunching characterized by autocorrelation function values of g(2) c (0) = 0.57±0.03<1. Comparing with a scaling model, the main noise source is found to be spontaneous Raman scattering in the cavity. This work opens a new possible means for realizing integrated nonclassical photon sources based on silica photonic circuits toward scalable quantum technologies.
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