Laser light with a Laguerre-Gaussian amplitude distribution is found to have a well-defined orbital angular momentum. An astigmatic optical system may be used to transform a high-order Laguerre-Gaussian mode into a high-order Hermite-Gaussian mode reversibly. An experiment is proposed to measure the mechanical torque induced by the transfer of orbital angular momentum associated with such a transformation.PACS number(s): 42.50.Vk

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We localize Cs atoms in wavelength-sized potential wells of an optical lattice, and cool them to a three-dimensional temperature of 700 nK by adiabatic expansion. In the optical lattice we precool the atoms to ഠ1 mK. We then reduce the trapping potential in a few hundred ms, causing the atomic center-of-mass distribution to expand and the temperature to decrease by an amount which agrees with a simple 3D band theory. These are the lowest 3D kinetic temperatures ever measured.

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