Efficiently Heralded Silicon Ring Resonator Photon-Pair Source

Presented here are results on a silicon ring resonator photon pair source with a high heralding efficiency. Previous ring resonator sources suffered from an effective 50% loss because, in order to generate the photons, the pump must be able to couple into the resonator which is an effective loss channel. However, in practice the optical loss of the pump can be traded off for a dramatic increase in heralding efficiency. This research found theoretically that the heralding efficiency should increase by a factor of 3.75 with a factor of 10 increase in the required pump power. This was demonstrated experimentally by varying the separation (gap) between the input waveguide and the ring while maintaining a constant drop port gap. The ring (R = 18.5 itm, W = 500 nm, and H = 220 nm) was pumped by a tunable laser (A R..- 1550 nm). The non-degenerate photons, produced via spontaneous four wave mixing, exited the ring and were coupled to fiber upon which they were filtered symmetrically about the pump. Coincidence counts were collected for all possible photon path combinations (through and drop port) and the ratio of the drop port coincidences to the sum of the drop port and cross term coincidences (one photon from the drop port and one from the through port) was calculated. With a 350 nm pump waveguide gap (2.33 times larger than the drop port gap) we confirmed our theoretical predictions, with an observed improvement in heralding efficiency by a factor of 2.61 (96.7% of correlated photons coupled out of the drop port). These results will enable increased photon flux integrated photon sources which can be utilized for high performance quantum computing and communication systems.