Dispersion engineered SiON ring resonators for integrated photon sources

The scientific interests on integrated photonic processors is growing rapidly, with the perspective of the realization of efficient and scalable quantum computation devices based on single photon qubits. While the on-chip single photon manipulation is well developed in quantum photonics circuits, the integration of photon generation and photon detection stages on the same chip is currently far from being established. In this work we present a scalable, integrated source of near-infrared photon pairs based on ring resonators, realized with dispersion-engineered silicon oxynitride waveguides.The use of high-index silicon oxynitride as core material gives the possibility to engineer the optical properties of the waveguides by adapting the ratio between oxygen and nitrogen in the deposition chamber, and allows the realization of films with thicknesses over 500nm without the formation of cracks. The realization of Four-Wave-Mixing in ring resonator requires a zero group-velocity-dispersion in order to have energy equidistant resonances. We show that, while it is almost impossible to achieve that condition with oxide-cladded SiON waveguides, the zero-dispersion-point in the red and near infrared wavelengths can be engineered if the waveguides are in direct contact with air. This can be achieved through a selective removal of the top oxide cladding from the ring resonators, by the means of wet etching and a silicon nitride etch-stop layer. We show that the realized devices are characterized by a constant Free Spectral Range at the engineered wavelengths and are feasible devices for nonlinear photon generation. The integration of the proposed sources with the already proven silicon integrated single-photon detectors (M. Bernard et al., Optica, 8(11), 1363-1364) could open the way to a fully integrated photonic processor, with all the components realized on a single chip, working at room temperature and potential for scalability.