Highly Coherent Room‐temperature Molecular Polariton Condensates

Abstract A growing number of organic materials have recently been reported to achieve room‐temperature exciton‐polariton (polariton) condensation, which is an essential requirement for practical polaritonic applications. Notably, fluorescent dyes utilizing the small‐molecule, ionic isolation lattice (SMILES) method have solved the long‐standing challenges of conventional organic dyes and have been successfully implemented in cavities to realize condensation. However, almost all demonstrations of molecular polariton condensates have inherently large spectral linewidth and poor temporal coherence arising from intrinsic disorder and low quality (Q) factor of the cavity. Here, exciton‐polaritons are realised using fluorescent dye SMILES in a high Q factor microcavity and we observe polariton condensates with a linewidth of 175 µeV. These polariton condensates exhibit temporal coherence of 30.3 ± 8.0 ps, indicating the highly coherent nature of the narrow linewidth condensates. These results set the stage for realizing highly coherent and robust polaritonic devices operating at room temperature.