Optical Cooling Techniques

P. A. Arsenev, E. F. Kustov, L. I. Surogin

Naomy Duarte Gomes, M. A. Caracanhas, Kílvia Mayre Farias +1 more

The technique of laser cooling, whose basic idea was proposed in 1975 [1], provided the development of many important areas like high-resolution spectroscopy [2], atomic clocks [3] and quantum gases confined in magnetic or optical traps [4, 5]. Among the techniques applied to cooling neutral atoms is the optical molasses [6] that will be explored in this work. Here we study the standard molasses and a new alternated molasses configuration, which consists of turning on just one pair of counter-propagating laser beams per cycle, and alternating this pair between the three spatial directions. We analyse the two techniques under the lens of the radiation force, by exploring a semiclassical treatment, in order to obtain the minimum energy attained by each of them at the end of the cooling process. We compare, then, these two cooling techniques, pointing out their advantages.

郁二 辻川

Maxime Arnal, V. Brunaud, Gabriel Chatelain +5 more

We report on a generic cooling technique for atoms trapped in optical lattices. It consists in modulating the lattice depth with a proper frequency sweeping. This filtering technique removes the most energetic atoms and provides, with the onset of thermalization, a cooling mechanism reminiscent of evaporative cooling. However, the selection is here performed in quasimomentum space rather than in position space. Interband selection rules are used to protect the population with a zero quasimomentum, namely the Bose Einstein condensate. Direct condensation of thermal atoms in an optical lattice is also achieved with this technique. It offers an interesting complementary cooling mechanism for quantum simulations performed with quantum gases trapped in optical lattices.

Anders Kastberg

Jonathan R. Gilbert, Rebekah Ferrier, Jacob Roberts

Abstract We present both the theoretical description and experimental implementation of a novel cooling technique for ultracold atoms trapped in a confining potential. We call the technique ‘spatially truncated optical pumping cooling.’ By using the fact that the internal states of atoms can be manipulated by laser light focused on only part of a confined ultracold gas, high energy atoms can be preferentially selected and then slowed to achieve cooling without requiring the loss of any atoms. This technique uses cooling photons more efficiently on a per photon basis than Doppler or polarization gradient cooling, while having approximately the same degree of difficulty with regard to experimental implementation.