Three dimensional cooling and trapping with a narrow line

Abstract

Abstract. The intercombination line of Strontium at 689nm is successfully used in laser cooling to reach the photon recoil limit with Doppler cooling in a magneto-optical traps (MOT). In this paper we present a systematic study of the loading efficiency of such a MOT. Comparing the experimental results to a simple model allows us to discuss the actual limitation of our apparatus. We also study in detail the final MOT regime emphasizing the role of gravity on the position, size and temperature along the vertical and horizontal directions. At large laser detuning, one finds an unusual situation where cooling and trapping occur in the presence of a high bias magnetic field.PACS. 3 9.25.+k

Scaling laws for large magneto-optical traps

“…As only this part of the atoms interacts with the cooling and trapping lasers, the trapping force has to be multiplied by p. The repulsive interaction between atoms requires a pair of atoms in the bright state and one thus has to include a factor p 2 in F ms . Consequently, the stationary atom density resulting from equations (21) and (22) has an additional p-dependence according to As this model is an extension of the one discussed in section 3.1, we call this the Wieman-Pritchard model.…”

Coherent flash of light emitted by a cold atomic cloud

“…A cold atomic sample of Strontium with up to 10 7 atoms in a volume of about 0.01 mm 3 , is produced in a magneto-optical trap on the 1 S 0 → 3 P 1 intercombination line at λ = 689 nm with a excited lifetime of Γ −1 = 21µs [8]. The minimal temperature of the sample is 0.7 µK which corresponds to kv ≃ 1.6Γ, where v is the mean atomic velocity (along any direction).…”

Fast and dense magneto-optical traps for strontium

“…The large discrepancy between red and blue transition linewidths makes it necessary to significantly broaden the linewidth of the red MOT laser to prevent atom loss: The Doppler-broadened linewidth ∆ω D = 2π × 4hΓ blue ln 2/(mλ 2 ) 2π × 0.9 MHz is ∼120 times larger than Γ. Furthermore, spatially confining atoms in a magneto-optical trap for the 1 S 0 -3 P 1 transition requires a magnetic quadrupole field with typical axial gradients B of a few G/cm [25][26][27][28]. This order-ofmagnitude reduction in magnetic field compared to the blue MOT has to be achieved on timescales comparable to the 1 S 0 refilling time to prevent atoms from escaping due to their per-axis atomic root-mean-square velocity ∼0.25 mm/ms.…”