Nonlinear self-action of ultrashort guided exciton-polariton pulses in dielectric slab coupled to 2D semiconductor

TL;DR

This study demonstrates strong nonlinear effects and solitonic pulse propagation in a hybrid waveguide system coupling a TMD monolayer with a dielectric slab, advancing the development of on-chip polaritonic devices.

Contribution

It provides the first experimental evidence of nonlinear spectral dependence and soliton formation in a TMD-based exciton-polariton waveguide system.

Findings

Observation of 36 meV Rabi splitting indicating strong coupling.

Demonstration of nonlinear spectral dependence on input pulse energy.

Confirmation of quasi-stationary solitonic pulse propagation.

Abstract

Recently reported large values of exciton-polariton nonlinearity of transition metal dichalcogenide (TMD) monolayers coupled to optically resonant structures approach the values characteristic for GaAs-based systems in the regime of strong light-matter coupling. Contrary to the latter, TMD-based polaritonic devices remain operational at ambient conditions and therefore have greater potential for practical nanophotonic applications. Here we present the study of the nonlinear properties of Ta$_2$O$_5$ slab waveguide coupled to a WSe$_2$ monolayer. We first confirm that the hybridization between waveguide photon mode and a 2D semiconductor exciton resonance gives rise to the formation of exciton-polaritons with Rabi splitting of 36 meV. By measuring transmission of ultrashort optical pulses through this TMD-based polaritonic waveguide, we demonstrate for the first time the strong nonlinear dependence of the output spectrum on the input pulse energy. Our theoretical model provides semi-quantitative agreement with experiment and gives insights into the dominating microscopic processes which determine the nonlinear pulse self-action: Coulomb inter-particle interaction and scattering to incoherent excitonic reservoir. We also confirm that at intermediate pump energies the system supports quasi-stationary solitonic regime of pulse propagation. Our results are essential for the development of nonlinear on-chip polaritonic devices based of 2D semiconductors.