Effective low-temperature photon gas through tunnel cooling

Light in optical microcavity have provided a platform that host numerous experiments studying thermalized photon gasses, among which is the Bose-Einstein
condensation of photons. Here, the thermal distribution of the photons is always
governed by the frequency-dependent gain and loss in this system, which in turn is given by the emission and absorption spectrum of the thermalized optical gain
medium. This links the photon temperature to the temperature of the optical medium. Studying phenomena at very low temperatures, in this approach, requires cooling the
medium with a cryostat, which can become unpractical and expensive.
In this work, we use a finite transverse trapping potential of the photon gas. The high energy modes of the system experience more tunneling losses than the low energy modes, thereby reducing the mean energy in the system. By fine-tuning this trapping potential, we can achieve frequency-dependent loss equivalent to a photon gas at cryogenic temperatures. We report on our recent progress towards realizing this in an experiment.