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Kerr-nonlinearity induced optical parametric oscillation in a microcavity is reported for the first time. Geometrical control of toroid microcavities enables a transition from stimulated Raman to optical parametric-oscillation regimes. Optical parametric oscillation is observed at record low threshold levels (174 micro-Watts of launched power) more than 2 orders of magnitude lower than for optical-fiber-based optical parametric oscillation. In addition to their microscopic size (typically tens of microns), these oscillators are wafer based, exhibit high conversion efficiency (36%), and are operating in a highly ideal "two photon" emission regime, with near-unity (0.97+/-0.03) idler-to-signal ratio.
Kippenberg et al. (Thu,) studied this question.