Second-harmonic generation in nonlinear plasmonic lattices enhanced by quantum emitter gain medium

TL;DR

This paper presents a theoretical and numerical study demonstrating that quantum emitter gain can significantly enhance second-harmonic generation in plasmonic nanostructures, with potential for high-efficiency nonlinear optical applications.

Contribution

It introduces a generalized driven-dissipative Tavis-Cummings model and combines it with numerical simulations to show gain-enhanced SHG in plasmonic lattices with quantum emitters.

Findings

Orders of magnitude increase in SHG efficiency with QE tuning

Gain facilitates strong enhancement of SHG in plasmonic structures

SHG efficiency depends on pump frequency and emitter resonance

Abstract

We report on theoretical study of second-harmonic generation (SHG) in plasmonic nanostructures interacting with two-level quantum emitters (QE) under incoherent energy pump. We generalize driven-dissipative Tavis-Cummings model by introducing anharmonic surface plasmon-polariton (SPP) mode coupled to QEs and examine physical properties of corresponding SPP-QE polariton states. Our calculations of the SHG efficiency for strong QE-SPP coupling demonstrate orders of magnitude enhancement facilitated by the polariton gain. We further discuss time-domain numerical simulations of SHG in a square lattice comprised of Ag nanopillars coupled to QEs utilizing fully vectorial nonperturbative nonlinear hydrodynamic model for conduction electrons coupled to Maxwell-Bloch equations for QEs. The simulations support the idea of gain enhanced SHG and show orders of magnitude increase in the SHG efficiency as the QEs are tuned in resonance with the lattice plasmon mode and brought above the population inversion threshold by incoherent pump. By varying pump frequency and tuning QEs to a localized plasmon mode, we demonstrate further enhancement of the SHG efficiency facilitated by strong local electric fields. The incident light polarization dependence of the SHG is examined and related to the symmetries of participating plasmon modes.