Berlin 2014 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 20: Quantum gases: Bosons I

Q 20.4: Talk

Tuesday, March 18, 2014, 11:30–11:45, UDL HS2002

Quantum Gases of Light in Variable Potentials — •David Dung, Tobias Damm, Julian Schmitt, Frank Vewinger, Jan Klärs, and Martin Weitz — Institut für Angewandte Physik, Universität Bonn

Bose-Einstein condensation, the macroscopic ground state occupation of bosonic particles at low temperature and high density, has previously been observed for cold atomic gases and solid state quasiparticles. In recent work, our group has realized Bose-Einstein condensation of photons in a dye-filled optical microcavity. In this experiment, a number conserving thermalization process is achieved by multiple absorption and fluorescence of dye-molecules. The microcavity modifies the photon dispersion and creates an effective trapping potential for photons. Formally, the system is equivalent to a two-dimensional gas of trapped, massive bosons.

We here report on current work to manipulate the environment of the photon gas by applying variable potentials. A trapping potential can be induced by locally changing the refractive index inside the microcavity. In the experiment this is realized by focused laser light that heats an absorptive thin film near the mirror surface. A thermo-responsive polymer mixed with the dye solution will undergo a phase-transition above a local temperature of 33°C and thereby change the refractive index significantly. The induced variable trapping potentials allow for the creation of multiple photon Bose-Einstein condensates on a lattice. More in the future, we plan to study topological phases and synthetic magnetic fields on the photonic lattice.