Hannover 2013 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 65: Quantum gases: Bosons III
Q 65.1: Gruppenbericht
Freitag, 22. März 2013, 14:00–14:30, F 342
Laser cooling to quantum degeneracy — •Simon Stellmer1, Benjamin Pasquiou1, Alex Bayerle1,2, Slava Tzanova1, Florian Vogl2, Rudolf Grimm1,2, and Florian Schreck1 — 1Institut für Quantenoptik und Quanteninformation, Innsbruck, Austria — 2Institut für Experimentalphysik und Forschungszentrum für Quantenphysik, Innsbruck, Austria
So far, every cooling method capable of reaching BEC in dilute gases relied on evaporative cooling as the last and crucial cooling stage. Laser cooling to BEC has been strongly discussed middle of the 1990s, but the experimental capabilities of that time were insufficient to reach this goal. Choosing strontium as the atomic species allows for a new approach.
We prepare a sample of 84Sr atoms in a large-volume reservoir dipole trap, constantly illuminated by cooling light on the narrow intercombination line that fixes the temperature to 800 nK. The density in the central region of the gas is increased by ramping up a dimple dipole trap. At the same time, we apply a transparency beam to this region of the sample. This beam is blue-detuned from a transition originating from the upper cooling state and selectively shifts this state out of resonance by 103 linewidths. Elastic collisions lead to a rapid accumulation of atoms in the dimple and ensure thermalization between the dimple and reservoir regions. A BEC of 105 atoms forms on a timescale of a few 10 ms. Laser cooling is the only cooling mechanism involved, while elastic collisions are indispensable for thermalization. This work holds prospects for the generation of a continuous atom laser.