Light-matter interaction and Bose-Einstein condensation of light

Abstract

The atom -electromagnetic field interaction is studied in the Dicke model, wherein a single field mode is interacting with a collection of two level atoms at thermal equilibrium. It is found that in the superradiant phase of the system, wherein the Bose-Einstein condensation of photons takes place, the notion of photon as an elementary electromagnetic excitation ceases to exist. The phase and intensity excitations of the condensate are found to be the true excitations of electromagnetic field. It is found that in this phase, the atom interacts with these excitations in a distinct coherent transition process, apart from the known stimulated emission/absorption and spontaneous emission processes. In the coherent transition it is found that while the atomic state changes in course of the transition process, the state of electromagnetic field remains unaffected. It is found that the transition probability of such coherent transition process is macroscopically large compared to other stimulated emission/absorption and spontaneous emission processes.

Classical-field description of Bose–Einstein condensation of parallel light in a nonlinear optical cavity*

“…[25,26] Furthermore, photons interact through an intermediate medium, e.g., photonic lattice and plasma have also been investigated. [27][28][29][30] It is well known that the Kerr-like nonlinear medium is a very important "laboratory" to study the quantum properties of photon gas. In this article, we aim at describing the Bose-Einstein condensation of parallel light in the 2D nonlinear optical cavity using the classical-field method.…”