Dynamics and correlations of a Bose–Einstein condensate of photons

Abstract

The Tutorial reports recent experimental advances in studies of the dynamics as well as the number and phase correlations of a Bose-Einstein condensed photon gas confined in a high-finesse dye-filled microcavity. Repeated absorption-emissionprocesses of photons on dye molecules here establish a thermal coupling of the photonic quantum gas to both a heat bath and a particle reservoir comprised of dye molecules. In this way, for the first time Bose-Einstein condensation under grand-canonical statistical ensemble conditions becomes experimentally accessible.

Cooperative phases and phase transitions of Bose condensed light in dye filled cavities

“…)responsible for absorbing and emitting photons. Such a variable emerges because the dye molecules are characterized by low symmetry so that the dipolar transition is non-degenerate, (see in [11,25]) and, thus, is described by a specific (positive or negative) direction determined by the spatial orientation of the molecule.…”

“…Creation of BEC of light [10][11][12][13][14], has opened up a new chapter in the search for strongly interacting phases of light. In these experiments the thermalization of light is achieved through absorption and reemission of photons by dye molecules which represent a thermal bath-thanks to their manifolds of rovibrational states exchanging energy with the solvent [15,16].…”

“…At this juncture it is important to mention that there are some similarities and significant differences between the dye molecules in the resonator [10,11,13,14] and excitons in the condensed matter systems [18,19] (see also in [20]). In the exciton-polaritonic materials the effective interaction between photons is induced through a direct exciton-exciton scattering-thanks to the linear and coherent coupling between exciton and photon branches of the spectrum.…”

“…Accordingly, the Gross-Pitaevskii (GP) equation including two polarizations of polaritons is straightforward to derive [21]. In the systems [10,11,13,14] the dye ensemble is disordered and, thus, it cannot be coherently coupled to photons. (The coherency and interaction between dye molecules via exchanging 2D-photons was discussed in [22].)…”

“…The experimentally achieved condensation of light is characterized by a weak effective interaction between photons [10,11,13,14]. However, even infinitesimally small interaction changes dramatically the properties of BEC (see in [23]).…”