Ultrafast transition from coherent to incoherent polariton nonlinearities in a hybrid 1L-WS2/plasmon structure

TL;DR

This study reveals ultrafast coherent to incoherent transition in hybrid 1L-WS2/plasmon polaritons, demonstrating significant nonlinear enhancement and potential for ultrafast optical switching using 2DES.

Contribution

It uncovers the ultrafast transition dynamics of polaritons in a hybrid monolayer WS2/plasmonic nanostructure using 2DES, highlighting their nonlinear properties and switching potential.

Findings

Over 20-fold enhancement of optical nonlinearity in hybrid structure

Rapid spectral evolution within ~70 fs indicating transition from coherence to incoherence

Potential for ultrafast all-optical switching applications

Abstract

Exciton polaritons based on atomically thin semiconductors are essential building blocks of quantum optoelectronic devices. Their properties are governed by an ultrafast and oscillatory energy transfer between their excitonic and photonic constituents, resulting in the formation of polaritonic quasiparticles with pronounced nonlinearities induced by the excitonic component. In metallic nanoresonators, dissipation phenomena limit the polariton lifetime to a few ten femtoseconds, so short that the role of these polaritons for the nonlinearities of such hybrids is yet unexplored. Here, we use ultrafast two-dimensional electronic spectroscopy (2DES) to uncover coherent polariton dynamics in a hybrid monolayer (1L) WS2/plasmonic nanostructure. With respect to an uncoupled WS2 flake, we observe an over 20-fold, polarization-dependent enhancement of the optical nonlinearity and a rapid evolution of the 2DES spectra within ~70 fs. We relate these dynamics to a transition from coherent polaritons to incoherent excitations, unravel the microscopic optical nonlinearities, and show the potential of coherent polaritons for ultrafast all-optical switching.