Abstract

Atoms in polarization-gradient cooling schemes arc optically pumped into a positiondependent state which forms a so-called spin grating. If the cooling fields also induce a periodic light-shift potential the atoms can instead become localized within small regions of the potential minima and thus give rise to spatial ordering of the atoms. Recently Birkl et al. [1] and Wcidemüller et al. [2] have used Bragg scattering to probe directly the localization and spatial order of atoms in a 3D optical lattice. The possibility of the observed Bragg reflection being caused by 4 wave mixing can be eliminated relatively easily [1,2]. It is more difficult, however, to distinguish between disordered atoms in a spin grating and spatially-ordered atoms localized about optical lattice points, especially in 1D lattices [3]. In this paper we propose a pulse-scattering method for probing the long-range spatial order in 1D lin ⊥ lin molasses which does distinguish between Bragg scattering from spatially-ordered atoms and a spin grating. We show that the scattering by the spin grating can be completely or partially filtered out by choosing the polarisation of the probe and the detector analyser.

© 1996 IEEE