Origins and control of the polarization splitting in exciton-polaritons microwires

TL;DR

This study investigates how anisotropic internal strains in 1D microcavities cause polarization-dependent energy splitting in exciton-polaritons, revealing tunable polarization states without dependence on wire width.

Contribution

It provides a detailed experimental analysis and a mechanical model explaining the origin and control of polarization splitting in exciton-polariton microwires.

Findings

Polarization splitting up to 1 meV observed in the lowest polariton branch.

Splitting results from anisotropic strains, not thermal effects.

Splitting and polarization can be tuned via exciton-photon detuning.

Abstract

We report on the experimental investigation of the polarization-dependent energy splitting in the lower exciton-polariton branches of a 1D microcavity. The splitting observed for the lowest branch can reach up to 1 meV. It does not result from low temperature thermal constraints but from anisotropic mechanical internal strains induced by etching. Those strains remove the degeneracy both in the photonic ($\delta E_{\mathrm{ph}}$) and excitonic ($\delta E_{\mathrm{exc}}$) components of the polariton but also in the photon-exciton coupling ($\delta\Omega$). Those three contributions are accurately infered from experimental data. It appears that the sign and magnitude of the polarization splitting as well as the linear polarization of the corresponding polariton eigenstates can be tuned through the bare exciton-photon detuning. Moreover, no dependence on the width of the wire (from 3 to 7 $\mathrm{\mu}$m) is observed. We propose a mechanical model explaining the universality of those observations paving the way to the engineering of polarization eigenstates in microwires exciton-polaritons.