Freiburg 2024 – scientific programme

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A: Fachverband Atomphysik

A 3: Bosonic Quantum Gases I (joint session Q/A)

A 3.2: Talk

Monday, March 11, 2024, 11:15–11:30, Aula

Nondegenerate two-photon absorption in gaseous xenon for Bose-Einstein condensation of vacuum-ultraviolet photons — •Thilo vom Hövel, Franz Huybrechts, Eric Boltersdorf, Frank Vewinger, and Martin Weitz — Institut für Angewandte Physik, Universität Bonn, Wegelerstr. 8, D-53115 Bonn

Motivated by work with cold atomic ensembles, Bose-Einstein condensation has in recent years also been realized for two-dimensional gases of visible-spectral-range photons. For this, e.g., a dye solution-filled optical microcavity is utilized to thermalize a photon gas via repeated cycles of absorption and emission by dye molecules. In previous work, we proposed to employ a similar platform for the construction of a coherent light source in the VUV (100 - 200 nm wavelength), a spectral range in which it is difficult to operate lasers.

For Bose-Einstein condensation of VUV photons, a thermalization mediator other than the dye system needs to be identified, as the latter is unsuitable in light of the high photon energies. One candidate is the quasimolecular xenon system, with absorption on the 5p⁶ → 5p⁵6s transition at 147 nm and emission on the Stokes-shifted second excimer continuum around 172 nm wavelength. In pure xenon at currently investigated pressures, however, the pronounced spectral gap between absorption and emission impedes efficient contact between photon gas and thermalization mediator. We here report on spectroscopic results of an experimental scheme devised to enhance the (re-)absorption of photons emitted around 172 nm, based on a nondegenerate two-photon process induced by the provision of an auxiliary photon field.

Keywords: VUV; Xenon; Bose-Einstein condensation; Two-photon absorption