Abstract

By intersecting four linearly polarized laser beams as shown in Fig. 1 we produce a three-dimensional optical lattice. In the interference pattern created by the beams there will be positions where the polarization is purely circular, σ⁺ or σ. At these points, optical pumping will put atoms in a state that has a potential minimum at the same location, due to the light shift. Thus, these points will constitute the lattice sites in a lattice of optical potential wells. With our particular configuration, the lattice will resemble a NaCl-crystal that is compressed in one dimension, see Fig. 1, with spacings .between neighbouring wells being $\text{λ*}\sqrt{2}/2$ and $\text{λ*}\sqrt{2}/4$ respectively (λ = 852 nm). To put atoms in these potential wells, we stop a thermal beam of cesium atoms, collect the atoms in a magneto-optical trap, and precool them in an optical molasses. The atoms then equilibrate in the optical lattice and get trapped in the wells. Typically, we populate 1% of the potential wells. We have studied the lattice in two independent ways: by observing the spectrum of resonance fluorescence emitted by the trapped atoms, and by turning off the lattice beams and measuring the thermal expansion of the atom cloud. Optical lattices have been studied by other groups by stimulated Raman spectroscopy with a probe beam.^1,2

© 1994 IEEE