Steady-state superfluidity of light in a tunable cavity at room temperature

TL;DR

This paper demonstrates room-temperature, steady-state superfluidity of light in a tunable cavity, achieved through thermo-optical nonlinearity, marking a significant advancement in photon superfluid research.

Contribution

First observation of steady-state superfluid cavity photons at room temperature using thermo-optical nonlinearity in an oil-filled cavity.

Findings

Suppression of backscattering above a critical intensity and below a critical velocity.

Room-temperature, steady-state photon superfluidity observed.

Numerical simulations support experimental results and reveal fluid reorganization within thermal relaxation time.

Abstract

Light in a nonlinear cavity is expected to flow without friction -- like a superfluid -- under certain conditions. Until now, part-light part-matter (i.e., polariton) superfluids have been observed either at liquid helium temperatures in steady state, or at room temperature for sub-picosecond timescales. Here we report signatures of superfluid cavity photons (not polaritons) for the first time. When launching a photon fluid against a defect, we observe a suppression of backscattering above a critical intensity and below a critical velocity. Room-temperature and steady-state photon superfluidity emerges thanks to the strong thermo-optical nonlinearity of our oil-filled cavity. Numerical simulations qualitatively reproduce our experimental observations, and reveal how a viscous photon fluid reorganizes into a superfluid within the thermal relaxation time of the oil. Our results establish thermo-optical nonlinear cavities as platforms for probing photon superfluidity at room temperature, and offer perspectives for exploring superfluidity in arbitrary potential landscapes using structured mirrors.