  Composite optical systems can show compelling collective dynamics. For
instance, the cooperative decay of quantum emitters into a common radiation
mode can lead to superradiance, where the emission rate of the ensemble is
larger than the sum of the rates of the individual emitters. Here, we report
experimental evidence of super spontaneous four-wave mixing (super SFWM), an
analogous effect for the generation of photon pairs in a parametric nonlinear
process on an integrated photonic device. We study this phenomenon in an array
of microring resonators on a silicon photonic chip coupled to bus waveguides.
We measured a cooperative pair generation rate that always exceeds the
incoherent sum of the rates of the individual resonators. We investigate the
physical mechanisms underlying this collective behaviour, clarify the impact of
loss, and address the aspects of fundamental and technological relevance of our
results.
