Degenerate parametric down-conversion facilitated by exciton-plasmon polariton states in nonlinear plasmonic cavity
The effect of degenerate parametric down-conversion (DPDC) is theoretically examined for the case of quantum emitters (QE) coupled via near-field interactions to a plasmonic nanostructure forming plasmonic cavity. We develop quantum driven-dissipative model to describe non-equilibrium dynamics of the system in which incoherently pumped QEs are tuned near second-harmonic response of the SPs. Our analysis shows that above critical SP-QE coupling rate, the system reaches strong coupling regime allowing for a lasing phase steady state. Properties of the exciton-plasmon polariton states formed as fluctuations above the steady state and in particular the effect of polariton facilitated DPDC are discussed. Differences in the polariton properties and DPDC power spectra originating from a finite size of QE ensemble and the model thermodynamic limit are identified.