Thermalization of Fluorescent Protein Exciton–Polaritons at Room Temperature

Abstract

Fluorescent proteins (FPs) have recently emerged as a serious contender for realizing ultralow threshold room temperature exciton–polariton condensation and lasing. This contribution investigates the thermalization of FP microcavity exciton–polaritons upon optical pumping under ambient conditions. Polariton cooling is realized using a new FP molecule, called mScarlet, coupled strongly to the optical modes in a Fabry–Pérot cavity. Interestingly, at the threshold excitation energy (fluence) of ≈9 nJ per pulse (15.6 mJ cm−2), an effective temperature is observed, Teff ≈ 350 ± 35 K close to the lattice temperature indicative of strongly thermalized exciton–polaritons at equilibrium. This efficient thermalization results from the interplay of radiative pumping facilitated by the energetics of the lower polariton branch and the cavity Q‐factor. Direct evidence for dramatic switching from an equilibrium state into a metastable state is observed for the organic cavity polariton device at room temperature via deviation from the Maxwell–Boltzmann statistics at k‖ = 0 above the threshold. Thermalized polariton gases in organic systems at equilibrium hold substantial promise for designing room temperature polaritonic circuits, switches, and lattices for analog simulation.

Embrace the darkness: An experimental perspective on organic exciton–polaritons

“…In one case, Satapathy et al reported thermalization of exciton-polaritons in a hybrid metaldielectric microcavity containing the fluorescent protein mScarlet. 181 Two samples were fabricated: one cavity with a Q-factor of 160 and another with a Q-factor of 330. When the low-Q sample was excited, the corresponding polariton distributions at different excitation fluences are well described by a Maxwell-Boltzmann distribution from 17.3 mJ/cm 2 up to the onset of photobleaching at 43.4 mJ/cm 2 [Fig.…”

Long-Range Propagation of Exciton-Polaritons in Large-Area 2D Semiconductor Monolayers

“…A promising means to enhance energy transport is to strongly couple excitons with photons forming quantum mechanical quasi-particles, called exciton-polaritons. , Conventional polaritonic structures employ planar microcavities where the optically active layer is embedded between metallic mirrors or distributed Bragg reflectors (DBRs). − However, their relatively short lifetimes and low group velocities prohibit propagation over long distances . In contrast, a truncated all-dielectric photonic structure can support long-range propagation of nondissipative Bloch surface waves (BSWs) over hundreds of micrometers .…”

Guided Bloch Surface Wave Polaritons on Patterned Distributed Bragg Reflectors at Room Temperature

“…The light–matter hybridization characteristics of polaritons can serve as an effective platform for both fundamental investigations and photonic device applications. − That is, devices that take advantage of the strong nonlinearities inherent in the exciton component, along with the propagation of the photon component, can usher in a new generation of highly capable and compact photonic devices. Fabry–Perot cavity polariton systems have shown coherent interference with confined polariton states over moderate propagation distances (∼25 μm). − However, a polariton condensate is required in those systems, which increases their complexity.…”