title: When does single-mode lasing become a condensation phenomenon?
abstract: We present a generic route to classical light condensation (LC) in linear photonic mode systems, such as cw lasers, with different grounds from regular Bose-Einstein condensation (BEC). LC is based on weighting the modes in a noisy environment (spontaneous emission, etc.) in a loss-gain scale, rather than in photon energy. It is characterized by a sharp transition from a multi- to single-mode oscillation. The study uses a linear multivariate Langevin formulation which gives a mode occupation hierarchy that functions like Bose-Einstein statistics. Condensation occurs when the spectral filtering has near the lowest-loss mode a power law dependence with exponent smaller than 1. We then discuss how condensation can occur in photon systems, its relation to lasing and the difficulties to observe regular photon-BEC in laser cavities. We raise the possibility that experiments on photon condensation in optical cavities fall in a classical LC or lasing category rather than being a thermal-quantum BEC phenomenon.
authors.affiliation: Department of Electrical Engineering, Technion, Haifa 32000, Israel. fischer@ee.technion.ac.il
authors.forename: Baruch
authors.initials: B
authors.lastname: Fischer
authors.forename: Rafi
authors.initials: R
authors.lastname: Weill
mesh_terms: D003198:Computer Simulation; D006801:Humans; D007834:Lasers; D017785:Photons; D011789:Quantum Theory; D012666:Semiconductors