Experimental Observation of Optically Trapped Atoms

TLDR

Sodium atoms cooled below 10⁻³ K in optical molasses are confined by a dipole‑force trap formed with a single, tightly focused Gaussian laser beam detuned several hundred gigahertz below the D₁ resonance. The experiment demonstrates the first observation of optically trapped atoms, confining roughly 500 atoms in a 10³ µm³ volume at densities of 10¹¹–10¹² cm⁻³, with lifetimes of several seconds limited by background pressure and matching theoretical predictions.

Abstract

We report the first observation of optically trapped atoms. Sodium atoms cooled below ${10}^{\ensuremath{-}3}$ K in "optical molasses" are captured by a dipole-force optical trap created by a single, strongly focused, Gaussian laser beam tuned several hundred gigahertz below the ${D}_{1}$ resonance transition. We estimate that about 500 atoms are confined in a volume of about ${10}^{3}$ \ensuremath{\mu}${\mathrm{m}}^{3}$ at a density of ${10}^{11}$-${10}^{12}$ ${\mathrm{cm}}^{\ensuremath{-}3}$. Trap lifetimes are limited by background pressure to several seconds. The observed trapping behavior is in good quantitative agreement with theoretical expectations.