  We report on four-wave mixing in coupled photonic crystal nano-cavities on a
silicon-on-insulator platform. Three photonic wire cavities are side-coupled to
obtain three modes equally separated in energy. The structure is designed to be
self-filtering, and we show that the pump is rejected by almost two orders of
magnitudes. We study both the stimulated and the spontaneous four-wave mixing
processes: owing to the small modal volume, we find that signal and idler
photons are generated with a hundred-fold increase in efficiency as compared to
silicon micro-ring resonators.
