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Laser Cooling and Trapping Group
Optical LatticesIn the figure below we show the optical potential the atoms experience as they move in a standing wave light field formed at the intersection of four laser beams. Laser cooling causes the atoms to lose enough energy that they become trapped in the egg-carton like potential wells. Because the periodic arrangement of trapping sites resembles a crystalline lattice, we call this system an optical lattice.
 
To establish the existence of this optical lattice we have performed a Bragg scattering experiment in which we observe the reflection of a probe laser beam as it coherently diffracts from our sample. Because the spacing in our lattice is on the micron scale (the wavelength of the trapping light) instead of the Angstrom scale, large-angle Bragg scattering occurs for visible light instead of x-rays. Our results include the frequency-dependence of the scattering and measurements of the lifetime of our lattice after the trapping light is extinguished. See G. Birkl, et al. Phys. Rev. Lett. 75, 2823 (1995). Current areas of research involve using Bragg scattering to explore the dynamics of atoms trapped in optical lattices, including approach to equilibrium, parametric driving, and the creation of breathing-mode wave packets.
Trey Porto Ian Spielman
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