Thermalization and condensation of a photon gas in everyday fibers and laser cavities

I will first briefly describe our work on Many-Body Photonics, that shows the role of noise and entropy in optics and lasers. An important example of this study reveals that mode-locking, which is one of the most important laser effects, is nothing but a first order phase transition. I then discuss several classical condensation phenomena in lasers, and finally describe recent experimental and theoretical results on  photon gas thermalization and lasing without an overall inversion that are unusual in lasers, and reach the possibility to observe quantum photon Bose-Einstein condensation (BEC) in standard fiber cavities at a room temperature. All these effects are done with regular erbium-doped fibers.