Precise angular deflection of thermal atomic beams by light

Abstract

In the early 1970s, various researchers showed that the force exerted by light on an atomic beam could deflect the beam. In particular, traveling wave light perpendicular to the beam could be used to impart velocity along the wave vector k of the light.1,2 In these experiments, the angular deflection of an atom depended on the interaction time between the atom and field and thus on the longitudinal velocity of the atoms; consequently, the resulting atomic beam had an increased angular divergence. Other experiments have demonstrated that light could be used to collimate an atomic beam.3 In this experiment we show that a 1-D spontaneous optical molasses nearly perpendicular to an atomic beam can be used to both collimate and angularly deflect an atomic beam, where the deflection is insensitive to longitudinal velocity. In fact, this technique decreases rather than increases the angular divergence of the initial beam. In our experiment we started with a 300°C thermal sodium atomic beam with an angular divergence of ~10 mrad. The light was detuned by Δ ≈ − 20 MHz from the 32S1/2 → 32P3/2 transition in sodium, which corresponds to twice the natural linewidth Γ. Using 1-D molasses formed from counterpropagating light beams of the 1/e waist size of the order of 3 mm, we were able to produce an atomic beam with an ~l-mrad divergence and an angular deflection of >10 mrad. The maximum possible angular deflection θ is of the order.