# Erlangen 2018 – scientific programme

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# Q: Fachverband Quantenoptik und Photonik

## Q 37: Quantum Gases (Bosons) IV

### Q 37.2: Talk

### Tuesday, March 6, 2018, 14:15–14:30, K 2.020

**Modeling Dye-Mediated Photon-Photon Interaction in Condensates of Light** — •Milan Radonjić^{1}, Wassilij Kopylov^{2}, Antun Balaž^{1}, and Axel Pelster^{3} — ^{1}Institute of Physics Belgrade, University of Belgrade, Serbia — ^{2}Department of Physics, Technische Universität Berlin, Germany — ^{3}Department of Physics and Research Center OPTIMAS, Technische Universität Kaiserslautern, Germany

Based entirely on the Lindblad master equation approach we obtain a microscopic description of photons in a dye-filled cavity, which features condensation of light [1,2]. To this end we generalize the nonequilibrium approach of Ref. [3] such that the dye-mediated contribution to the photon-photon interaction in the light condensate is accessible. We describe the dynamics of the system by analyzing the resulting equations of motion. In particular, we discuss the existence of two limiting cases for steady states: photon BEC and laser-like. In the former case, we determine the corresponding dimensionless interaction strength relying on realistic experimental data and find a good agreement with the previous theoretical estimate [4]. Furthermore, we investigate how the dimensionless interaction strength depends on the respective system parameters such as the effective temperature of the dye and the number of the dye molecules.

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

[2] R. A. Nyman and M. H. Szymanska, Phys. Rev. A **89**, 033844 (2014)

[3] P. Kirton and J. Keeling, Phys. Rev. Lett. **111**, 100404 (2013)

[4] E. C. I. van der Wurff et al., Phys. Rev. Lett. **113**, 135301 (2014)