Emulation of lossless exciton-polariton condensates by dual-core optical waveguides: Stability, collective modes, and dark solitons

TL;DR

This paper demonstrates how dual-core optical waveguides can emulate lossless exciton-polariton condensates, analyzing their stability, collective excitations, and the formation of dark solitons, providing a new platform for studying polariton physics.

Contribution

The study introduces a novel optical dual-core waveguide setup to simulate lossless exciton-polariton systems, analyzing stability and excitations, which was not previously feasible in microcavities.

Findings

Lower-branch state is stable against small perturbations.

Upper-branch state is always modulationally unstable.

Stable 1D states can support dark solitons.

Abstract

We propose a possibility to simulate the exciton-polariton (EP) system in the lossless limit, which is not currently available in semiconductor microcavities, by means of a simple optical dual-core waveguide, with one core carrying the nonlinearity and operating close to the zero-group-velocity-dispersion (GVD) point, and the other core being linear and dispersive. Both 2D and 1D EP systems may be emulated by means of this optical setting. In the framework of this system, we find that, while the uniform state corresponding to the lower branch of the nonlinear dispersion relation is stable against small perturbations, the upper branch is always subject to the modulational instability (MI). The stability and instability are verified by direct simulations too. We analyze collective excitations on top of the stable lower-branch state, which include a Bogoliubov-like gapless mode and a gapped one. Analytical results are obtained for the corresponding sound velocity and energy gap. The effect of a uniform phase gradient (superflow) on the stability is considered too, with a conclusion that the lower-branch state becomes unstable above a critical wavenumber of the flux. Finally, we demonstrate that the stable 1D state may carry robust dark solitons.