Cooling all external degrees of freedom of optically trapped chromium atoms using gray molasses

Abstract

We report on a scheme to cool and compress trapped clouds of highly magnetic 52 Cr atoms. This scheme combines sequences of gray molasses, which freeze the velocity distribution, and free evolutions in the (close to) harmonic trap, which periodically exchange the spatial and velocity degrees of freedom. Taken together, the successive gray molasses pulses cool all external degrees of freedom, which leads to an increase of the phase-space density (P.S.D.) by a factor of ≈ 250, allowing to reach a high final P.S.D. of ≈ 1.7 −3 . These experiments are performed within an optical dipole trap, in which gray molasses work equally well as in free space. The obtained samples are then an ideal starting point for the evaporation stage aiming at the quantum regime.

Enhancing fiber atom interferometer by in-fiber laser cooling

“…CPT occurs in a threelevel -type system coupled to two coherent resonant light fields. Atoms in the bright state of CPT lose the kinetic energy by climbing up the optical potential from the light fields and are optically pumped into the dark state where atoms are decoupled from the light fields [16][17][18].…”

Enhancing fiber atom interferometer by in-fiber laser cooling

“…Each beam includes two frequencies f 1 (pump) and f 2 (repump) which are +20 MHz detuned from 85 Rb D1 line F = 2 to F ′ = 3 and F = 3 to F ′ = 3 transitions, respectively. When these two frequencies are phase coherent, a dark-state formed by a superposition of F = 2 and F = 3 is created to enhance the cooling efficiency [11,12]. The power ratio of the two frequencies is 35 to ensure all the atoms are accumulated in the F = 2 state after 3.2 ms of gray molasses.…”

Fast and High-Yield Loading of a D$_2$ MOT of Potassium from a Cryogenic Buffer Gas Beam

“…The near-universality of CBGBs makes them especially useful for producing ultracold refractory atoms, which have low vapor pressures and thus require very high oven temperatures. Laser cooling pathways have been identified in refractory species such as chromium [72][73][74][75][76], titanium, zirconium, vanadium, niobium, manganese, technetium, and ruthenium, in addition to other atoms with low vapor pressures [77]. An active experimental effort is underway toward a MOT of titanium [78].…”