Hannover 2013 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 12: Quantum gases: Bosons I

Q 12.1: Group Report

Monday, March 18, 2013, 14:00–14:30, E 001

Intensity correlations of a Bose-Einstein condensate of photons in a dye-filled microcavity — •Julian Schmitt, Tobias Damm, David Dung, Cesar Cabrera, Frank Vewinger, Jan Klaers, and Martin Weitz — Institut für Angwandte Physik, Universität Bonn, Wegelerstraße 8, 53115 Bonn

We have measured second-order time correlations within a Bose-Einstein condensate of photons inside a dye-filled optical microcavity. In our experiment, photons are thermally equilibrated by multiple absorption-fluorescence cycles in a dye medium, which constitutes both a heat bath and a particle reservoir [1]. Due to the excitation exchange between the photon gas and the dye molecule reservoir, grand canonical experimental conditions are expected to be realized in the system [2]. Under these conditions, unusually large fluctuations of the condensate number (fluctuation catastrophe) are expected [3], where the photon number distribution is Bose-Einstein-like. We experimentally observe a bunching of the condensed photons, which we attribute as evidence for a grand canonical BEC regime. On the other hand, for large condensate fractions due to the finite size of the molecular reservoir a transition to the usual canonical condensate regime occurs, for which Poissonian number fluctuations lead to second order coherence. Our observations are in agreement with theoretical predictions.
J. Klaers, J. Schmitt, F. Vewinger, M. Weitz, Nature 468, 545(2010)
J. Klaers, J. Schmitt, T. Damm, F. Vewinger, M. Weitz, Phys. Rev. Lett. 108, 160403 (2012)
e.g. R. Ziff, G. Uhlenbeck, M. Kac, Phys. Rep. 32, 169 (1977)