Berlin 2014 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 20: Quantum gases: Bosons I

Q 20.1: Group Report

Tuesday, March 18, 2014, 10:30–11:00, UDL HS2002

Thermalization dynamics and the formation of a photon Bose-Einstein condensate emerging from a laser-like state — •Julian Schmitt, Tobias Damm, David Dung, Frank Vewinger, Jan Klaers, and Martin Weitz — Institut für Angewandte Physik, Universität Bonn, D-53115 Bonn, Deutschland

Dissipation and losses are known to be able to drive a physical system out of equilibrium. A prominent example for a system dominated by dissipative effects is the laser, where one engineers photon loss inside an optical resonator to achieve a large population of a selected resonator mode. This is in contrast to an ensemble thermalizing faster than that particles are lost, where thermodynamic equilibrium is reached and the system - under appropriate conditions - undergoes Bose-Einstein condensation (BEC) into the system ground state. Here we report a study of the thermalization dynamics of a photon gas trapped in a high-finesse dye microcavity, where thermal and chemical equilibrium is established by contact to the dye reservoir. We have carried out time-resolved measurements of the spatial and spectral photon dynamics with a streak camera. We find that the equilibration time is determined by the photon reabsorption time in the dye microcavity. Further, we observe the coherent oscillation of a laser-like wave packet inside the harmonic trap, which eventually collapses into a Bose-Einstein condensate as photons are reabsorbed and emitted by the dye molecules and reach thermal equilibrium. Our results show a dissipation-controlled crossover between a laser-like state and a photon BEC.