Impact of Backscattering in Silicon Micro-ring Resonators on Photon Pair Generation

Backscattering in silicon micro-ring resonators is due to the side wall roughness of the waveguides, which leads to the backward coupling of light to the counter-propagating modes. In this paper, the impact of backscattering on the photon pair generation in a silicon micro-ring resonator with a quality factor (Q) of similar to 10(4) is investigated experimentally. It shows that due to the effect of backscattering, the two photons in a pair not only output from the resonator forwardly, but also both output backwardly, or even one forwardly and the other backwardly. Analysis on the coincident counts of different output port combinations shows that the effect of the pump light reflection due to the backscattering is weak. The reason for that the photon pairs output from all the port combinations is mainly due to the reflection of the generated signaL/idler photons by the backscattering in the resonator. The experiments of Franson-type interference are taken to investigate the property of energy-time entanglement in the photon pairs outputting from different directions. The experiment results show that the backscattering may impact the interference fringes, however, energy-time entanglement exists in all the cases under our experiment condition.