Continuous polarization-gradient precooling-assisted velocity-selective coherent population trapping

Laser Cooling: Beyond One Field and One Dimension

“…[21]. We have also carried out experiments and calculations which show that the velocity dependent Raman force can produce efficient cooling [22,23]. In fact, at low velocities, the cooling is much stronger than Fig.…”

“…These effects depend on the mixing [12] of the two SW fields in the atom-field interaction and cannot be explained in a simple two-level-like model. The prediction and observation of the cooling is of particular interest because it can be used to greatly enhance the capture rate of atoms by the"zero" velocity trapped state [23]. Experiments are currently under way in our laboratory to build a novel three-dimensional dark-state trap which takes advantage of this process.…”

Sisyphus Cooling and Subrecoil Cooling

“…In the o + -o~ configuration, the friction forces can be experienced by very slow atoms. 14 combined effect of the rotation of the polarization and of (iii) The last point concerns the importance of polariza-optical pumping and light shifts produces a highly sensitive tion gradients. Long pumping times can give rise to large motion-induced population difference among the Zeeman friction forces only if the internal atomic state in g strongly sublevels of g (defined with respect to the axis of the standdepends on the position of the atom in the laser wave, so that ing wave) and, consequently, a large imbalance between the when the atom is moving there are large changes in its inter-radiation pressures of the two counterpropagating waves, nal state and, consequently, large nonadiabatic effects.…”

Population accumulation in dark states and subrecoil laser cooling

“…The m~= 0~m = 0 transition is forbidden, so that atoms eventually depopulate the V system and only occupy the A system. and linJ lin polarizations applied to a Jg = 1 -+ J = 1 transition, as found in metastable helium for 2 Sg 2sPq [2,5,9]. Thus it is not expected that the sign of b, where b = u~-is the laser detuning &om the atomic resonance &equency, will aAect the cooling process, as it does in laser cooling caused by a damping force.…”

“…Thus it is not expected that the sign of b, where b = u~-is the laser detuning &om the atomic resonance &equency, will aAect the cooling process, as it does in laser cooling caused by a damping force. Indeed, it has been found both theoretically and experimentally that VSCPT is eKcient independently of the sign of the detuning [2,5,9,10]. Nevertheless, in [2] a difference in the finite-time ground-state momentum distribution 'P(pg, t) about p~= 0 was found to be associated with the sign of h. The momentum distribution between the characteristic narrow VSCPT cold peaks in P(pg, t) at ps = khk was elevated for positive detuning and depressed for negative detuning (see Fig.…”