From Classical Four-Wave Mixing to Parametric Fluorescence in Silicon   micro-ring resonators
  Four-wave mixing can be stimulated or occur spontaneously. The first process is intrinsically much stronger, and well understood through classical nonlinear optics. The latter, also known as parametric fluorescence, can be explained only in the framework of a quantum theory of light. We experimentally demonstrate that, in a micro-ring resonator, there exists a simple relation between the efficiencies of these two processes, which is independent of the nonlinearity and size of the ring. In particular we show that the average power generated by parametric fluorescence can be immediately estimated from a classical FWM experiment. These results suggest that classical nonlinear characterization of a photonic integrated structure can provide accurate information on its nonlinear quantum properties. 
Stefano Azzini, Davide Grassani, Matteo Galli, Lucio Claudio Andreani,   Marc Sorel, Michael J. Strain, L. G. Helt, J. E. Si...
quant-ph cond-mat.mtrl-sci physics.optics