Plasmon exciton-polariton lasing

Strong light-matter interaction leads to the appearance of new states, i.e. exciton-polaritons, with photophysical properties rather distinct from their constituents. Recent developments in fabrication techniques allow us to make metallic structures with strong electric field confinement in nanoscale mode volumes, allowing for a facile assembly of strongly coupled systems at room temperature based on a hybrid organic-plasmonic architecture. In this research, a planar array of metallic nano-antennas is covered by a polymer layer doped with organic molecules, achieving strong coupling of organic excitons with collective plasmonic resonances in the array. We use photoluminescence spectroscopy to measure an onset in nonlinear emission and polariton lasing in this system. At increasing molecular doping levels we observe an increase of the Rabi splitting caused by strong coupling and a concomitant decrease in the lasing threshold. This behavior is observed in spite of a strong reduction in the photoluminescence lifetime and the quantum yield of the dye. Using angular resolved photoluminescence spectroscopy, we measure the thermalization and condensation of plasmon-exciton-polaritons (PEPs) into a mode which is dark in the linear regime. These measurements can be interpreted in terms of stimulated scattering of PEPs at room temperature in the open cavity defined by the nano-antenna array [1, 2]. The lowest threshold that we measure is lower than previous values reported at room temperature in organic materials using microcavities. These results illustrate the potential of metamaterials and plasmonic systems for polariton lasing in spite of the inherent losses of metals.