Laser light condensation phenomenon

The interesting question if and how can Bose-Einstein condensation (BEC) occur with photons has received a boost by a recent experiment that reported on the observation of photon-BEC condensation in an optical microcavity [1]. Here we present a different laser light condensation (LC) phenomenon [2], while discussing and questioning the meaning and the possibility to observe thermal photon-BEC in laser cavities. LC is a classical condensation effect that is based on very different grounds than the regular BEC. Its “energy” levels are measured in a loss-gain scale inherent in laser cavities, where the “ground-state” is the lowest-loss mode, and noise has the role of temperature. The loss scale gives a power occupation hierarchy and power spectra similar to Bose-Einstein statistics with an effective chemical potential parameter and eventually laser light-condensation (LC) which is formally very similar to BEC in a potential-well [3].