Microring resonators are attractive for low-power frequency conversion via Bragg-scattering fourwave-mixing due to their comb-like resonance spectrum, which allows resonant enhancement of all four waves while maintaining energy and momentum conservation. However, the symmetry of such mode structures limits the conversion efficiency to 50% due to the equal probability of up- and down-conversion. Here, we demonstrate how two coupled microrings enable highly directional conversion between the spectral modes of one of the rings. An extinction between up- and down-conversion of more than 40 dB is experimentally observed. Based on this method, we propose a design for on-chip multiplexed single-photon sources that probabilistically generate photon pairs across many frequency modes of a ring resonator and subsequently convert them to a single frequency-thereby enabling quasi-deterministic photon emission. Our numerical analysis shows that once a photon is generated, it can be converted and emitted into a wave packet having a 90% overlap with a Gaussian with 99% efficiency for a ratio between intrinsic and coupling quality factors of 400.
- Single photon source
- Quantum information technology
- Frequency conversion
Heuck, M., Koefoed, J. G., Christensen, J. B., Ding, Y., Frandsen, L. H., Rottwitt, K., & Oxenløwe, L. K. (2019). Unidirectional frequency conversion in microring resonators for on-chip frequency-multiplexed single-photon sources. New Journal of Physics, 21(3), [033037 ]. https://doi.org/10.1088/1367-2630/ab09a7