Second Harmonic Generation from a Single Plasmonic Nanorod Strongly Coupled to a WSe2 Monolayer

TL;DR

This paper demonstrates second harmonic generation from a WSe2 monolayer strongly coupled to a gold nanorod, revealing nonlinear optical properties crucial for quantum photonic applications.

Contribution

First experimental observation of nonlinear second harmonic generation in a strongly coupled WSe2 monolayer and plasmonic nanorod system, supported by numerical simulations.

Findings

Observation of second harmonic signal with frequency splitting

Coupled oscillator model explains the nonlinear response

Numerical simulations match experimental results

Abstract

Monolayer transition metal dichalcogenides, coupled to metal plasmonic nanocavities, have recently emerged as new platforms for strong light-matter interactions. These systems are expected to have nonlinear optical properties that will enable them to be used as entangled photon sources, compact wave-mixing devices, and other elements for classical and quantum photonic technologies. Here we report the first experimental investigation of the nonlinear properties of these strongly coupled systems, by observing second harmonic generation from a WSe2 monolayer strongly coupled to a single gold nanorod. The pump frequency dependence of the second harmonic signal displays a pronounced splitting that can be explained by a coupled oscillator model with second-order nonlinearities. Rigorous numerical simulations utilizing a nonperturbative nonlinear hydrodynamic model of conduction electrons support this interpretation and reproduce experimental results. Our study thus lays the groundwork for understanding the nonlinear properties of strongly coupled nanoscale systems.