Stuttgart 2012 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 5: SAMOP Dissertation Prize Symposium

A 5.2: Hauptvortrag

Montag, 12. März 2012, 14:30–15:00, V47.01

Bose-Einstein condensation of photons — •Jan Klärs — Institut für Angewandte Physik, Universität Bonn, Germany

Does a photon gas condense at low temperatures? Black-body radiation, presumably the most omnipresent Bose gas at all, does not show a phase transition at low temperatures. Here, temperature and photon number cannot be tuned independently. If the temperature of the photon gas is lowered, then also the photon number will decrease (Stefan-Boltzmann law). Under these conditions, a condensation, i.e. a macroscopic occupation of the cavity ground mode, will not occur.

Here, I report on experiments with a two-dimensional photon gas in a dye-filled optical microcavity. In this system, the two transversal motional degrees of freedom of the photons are thermally coupled to the cavity environment by multiple absorption-emission cycles in the dye medium. The cavity mirrors provide an effective photon mass and a confining potential, making the system formally equivalent to a two-dimensional gas of trapped, massive bosons. For such a system, a Bose-Einstein condensation is expected to set in at low temperatures or high photon densities. I will discuss experiments that demonstrate both the thermalization and the condensation process.