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Q: Fachverband Quantenoptik und Photonik

Q 2: Quantum Gases: Bosons 1

Q 2.5: Vortrag

Montag, 14. März 2011, 11:30–11:45, HÜL 386

Bose-Einstein condensation of photons in an optical microcavity — •Jan Klärs, Julian Schmitt, Frank Vewinger, and Martin Weitz — Institut für Angewandte Physik, Universität Bonn

Bose-Einstein condensation has been observed in several physical systems, including cold atomic gases and solid-state quasiparticles. However the most omnipresent Bose gas, blackbody radiation, does not show BEC. In such systems the photon number is not conserved when the temperature of the photon gas is varied; at low temperatures, photons disappear in the cavity walls instead of occupying the cavity ground state. A number-conserving thermalization process was experimentally observed for a two-dimensional photon gas in a dye-filled optical microcavity [1]. Here we report the observation of a Bose-Einstein condensate of photons in this system [2]. The cavity mirrors provide both a confining potential and a non-vanishing effective photon mass, making the system formally equivalent to a two-dimensional gas of trapped, massive bosons. The photons thermalize to the temperature of the dye solution (room temperature) by multiple scattering with the dye molecules. Upon increasing the photon density, we observe the following BEC signatures: the photon energies have a Bose-Einstein distribution including a massively populated ground-state mode; the phase transition occurs at the expected photon density and exhibits the predicted dependence on cavity geometry; and the ground-state mode emerges even for a spatially displaced pump spot.

[1] J. Klaers, F. Vewinger and M. Weitz, Nature Phys. 6, 512 (2010)

[2] J. Klaers et al., Nature 468, 545 (2010)