Nonlinear optics at exciton-plasmon interfaces | Maxim Sukharev

Ensembles of quantum emitters optically coupled to plasmonic nanocavities, have recently emerged as new platforms for strong light-matter interactions. These systems can be potentially used as nonlinear elements in optical quantum technologies and photonic circuits as entangled photon sources, compact wave mixing devices. However, their nonlinear properties have not been rigorously studied so far. In this talk
I will discuss the nonlinear dynamics of quantum emitters strongly coupled to plasmonic materials of various geometries. The employed model relies on coupled hydrodynamic-Maxwell-Bloch equations considered in three dimensions and propagated in time domain. This model combines the nonlinear response from both metal and emitters. Such an approach allows us to scrutinize fast dynamics of polaritonic states and characterize contributions of the strong coupling to nonlinear optical phenomena such as second harmonic generation (SHG). I will discuss the first observation of SHG from atomically thin WSe2 strongly coupled to a single gold nanorod. Remarkably, the pump-frequency dependence of SHG signals displays a pronounced splitting, which can be explained by a coupled-oscillators model with second order nonlinearities. The second part of my talk pertains to the theoretical study of SHG in periodic arrays of nanopillars interacting strongly with ensembles of quantum emitters under incoherent pump. Calculations of the SHG efficiency for strong emitters-plasmon coupling demonstrates orders of magnitude enhancement facilitated by the polariton gain. I will also discuss recent advances in understanding of physics of SHG by periodic hexagonal arrays of triangular nanoholes.