U. Vogl | Searcharxiv

arXiv2015

Laser-induced cooling of broadband heat reservoirs

We explore, theoretically and experimentally, a method for cooling a broadband heat reservoir, via its laser-assisted collisions with two-level atoms followed by their fluorescence. This method is shown to be advantageous compared to existing laser-cooling methods in terms of its cooling efficiency, the lowest attainable temperature for broadband baths and its versatility: it can cool down any heat reservoir, provided the laser is red-detuned from the atomic resonance. It is applicable to cooling down both dense gaseous and condensed media.

quant-ph↗

arXiv2010

Thermalization of coupled atom-light states in the presence of optical collisions

The interaction of a two-level atomic ensemble with a quantized single mode electromagnetic field in the presence of optical collisions (OC) is investigated both theoretically and experimentally. The main accent is made on achieving thermal equilibrium for coupled atom-light states (in particular dressed states). We propose a model of atomic dressed state thermalization that accounts for the evolution of the pseudo-spin Bloch vector components and characterize the essential role of the spontaneous emission rate in the thermalization process. Our model shows that the time of thermalization of the coupled atom-light states strictly depends on the ratio of the detuning and the resonant Rabi frequency. The predicted time of thermalization is in the nanosecond domain and about ten times shorter than the natural lifetime at full optical power in our experiment. Experimentally we are investigating the interaction of the optical field with rubidium atoms in an ultra-high pressure buffer gas cell under the condition of large atom-field detuning comparable to the thermal energy in frequency units. In particular, an observed detuning dependence of the saturated lineshape is interpreted as evidence for thermal equilibrium of coupled atom-light states. A significant modification of sideband intensity weights is predicted and obtained in this case as well.

cond-mat.mes-hall↗

arXiv2007

Spectroscopy of atomic rubidium at 500 bar buffer gas pressure: approaching the thermal equilibrium of dressed atom-light states

We have recorded fluorescence spectra of the atomic rubidium D-lines in the presence of several hundreds of bars buffer gas pressure. With additional saturation broadening a spectral linewidth comparable to the thermal energy of the atoms in the heated gas cell is achieved. An intensity-dependent blue asymmetry of the spectra is observed, which becomes increasingly pronounced when extrapolating to infinitely high light intensity. We interpret our results as evidence for the dressed (coupled atom-light) states to approach thermal equilibrium.

physics.atom-ph↗