High-Chirality Polariton Lasing from Symmetry-Broken Plasmonic Lattices

Chiral polariton lasing is a source of circularly polarized, energy-efficient coherent emission. However, generating high optical contrast of opposite handedness is challenging because excitonic gain materials show low circular dichroism at room temperature. In addition, highly chiral lasing requires the symmetry of the optical cavities to be broken, which can affect the resonance quality and result in low-chiral purity. Here, we report how plasmonic nanoparticle lattice cavities having mismatched dimer unit cells strongly coupled to CdSe nanoplatelets can facilitate polariton lasing with low threshold fluences (8 μJ/cm²) and high chiral purity (∼0.92). This lasing threshold is at least two times lower than that of other systems at room temperature, and the chirality approaches the theoretical maximum. These room-temperature characteristics are promising for using chiral polariton lasing in a broad range of applications, from spintronics to optoelectronics to quantum information processing.