Abstract

The light shifts of an atom in a standing wave are generally space dependent because of the gradient of polarization or intensity in the standing wave. These spatially modulated light shifts appear as a periodic optical potential in which quantization of atomic motion can occur. Recent experiments^1–3 showed the occurrence of quantized vibrational states for the external degrees of freedom in two types of one-dimensional (1D) optical molasses: the first consisted of two linearly cross-polarized counterpropagating beams,^1,2 and the second consisted of two circularly polarized beams in the presence of a transverse magnetic field.³ Transition between quantized vibrational states was observed by stimulated^1,3 and spontaneous² Raman spectroscopy. Furthermore, these experiments demonstrated that a long-range spatial order similar to that found in crystals but with a spatial period of the order of the optical wavelength is obtained. These experiments also showed the occurrence of very long damping times (much longer than the optical pumping time⁴) associated with the evolution of the external degrees of freedom.

© 1993 Optical Society of America