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MO: Fachverband Molekülphysik

MO 12: Poster – Cold Atoms and Molecules, Matter Waves (joint session Q/A/MO)

MO 12.6: Poster

Dienstag, 11. März 2025, 14:00–16:00, Tent

Cascaded Nonlinearities for Effectively Interacting Bose-Einstein Condensates of Photons — •Niels Wolf, Andreas Redmann, Christian Kurtscheid, Frank Vewinger, Julian Schmitt, and Martin Weitz — Institut für Angewandte Physik, Bonn, Deutschland

Bose-Einstein condensation has been observed in ultracold atomic gases, polaritons, and, more recently, in low-dimensional photon gases. Since the photon-photon interaction is vanishingly small, thermalization of photons, e.g. as dye microcavity photon condensates in the latter systems, is achieved not through particle-particle collisions, but rather via contact with a reservoir, here the dye molecules [1]. Nevertheless, strong photon-photon interactions, such as effective Kerr interactions induced by cascaded second-order nonlinearities, could enable the realization of an interacting photon Bose-Einstein condensate. This could, e.g. open pathways to generating highly entangled photon states by purely thermodynamical methods [2]. We employ a triply resonant optical parametric oscillator setup with independent control over pump and subharmonic wavelength cavities. This configuration enables the generation of cascaded second-order nonlinearities, producing a phase shift potentially stronger than that of direct Kerr interaction. Suitable frequency filtering is crucial to tune the optical parametric oscillator to degeneracy, which is essential for fully characterizing the phase shift and determining the effective Kerr coefficient.

[1] J. Klaers et al., Nature 468, 545 (2010) [2] C. Kurtscheid et al., Science 366, 894 (2019)

Keywords: Bose-Einstein Condensation of Photons; Interacting Photon Gases; Effektive Kerr-Effect; Optical Parametric Oscillator Dynamics; Cascaded Second Order Nonlinearities