Cavity exciton-polariton condensates in engineered potential landscapes at room temperature

Abstract

We create exciton-polariton (strongly coupled light-matter quasi particles) Bose-Einstein condensates at room temperature [1] by optically exciting a ladder-type conjugated polymer [2] placed inside a tuneable Fabry-Perot microcavity [3]. By Focussed Ion Beam (FIB) milling we fabricate different structure for in-plane confinement, ranging from 0D (single Gaussian-shaped defect) to 2D ones (arrays of coupled Gaussian defects). In the first part of this work we focus on the basic building blocks of our system, the strong light-matter coupling and the exciton-polariton condensation localized in a 0D Gaussian-shaped defect structure. The strong coupling between the excitonic resonance of the conjugated polymer and the individual cavity modes is obtained by exciting the system while detuning the cavity length till the anti-crossing behaviour of the modes appears. By increasing the excitation power above threshold, we reach room temperature condensation in a single Gaussian defect. The condensation features are demonstrated by showing non-linear emission intensity, spectral line-narrowing and a characteristic blue shift as function of excitation power. To better characterize the condensation in such a system, we studied the angular emission (Fig. 1 (a) and (b)) and the first order coherence (Fig. 1 (c) and (d)) of the exciton-polaritons below and above threshold.