Stuttgart 2012 – scientific programme

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A: Fachverband Atomphysik

A 8: Kalte Atome: Fallen und Kühlung

A 8.3: Talk

Monday, March 12, 2012, 17:00–17:15, V7.02

Shaping the evanescent field of an optical nano-fiber for cold atom trapping — •Ciaran Phelan, Tara Hennessy, and Thomas Busch — Physics Department, University College Cork, Cork, Ireland / Quantum Systems Unit, OIST, Okinawa, Japan

Optical nano-fibers have a number of striking properties which have recently led to their use as a means of trapping neutral atoms. The small diameter of the fiber results in most of the power transmitted in the fiber being contained in the evanescent field. Furthermore, the confinement of the guided fiber modes means that the fiber mode can maintain its profile over a much greater distance than the Rayleigh range of the equivalent free space mode.

Recently, a number of schemes for trapping neutral atoms in the evanescent field have been proposed. One of these involves combining the effect of a red detuned (with respect to the trapped atom's transition frequency) attractive field and a blue detuned repulsive field to form a cylindrical potential minimum surrounding the fiber.

By counter-propagating two red detuned fiber modes with opposite helical phase terms, an interference pattern is formed in the evanescent field. This, when combined with a repulsive fundamental mode, causes the splitting of the circularly symmetric ring trap into an array of traps located on a circle surrounding the fiber. This one dimensional array of traps, with sub-wavelength spacing between the traps has the potential to form a Mott insulator on a ring surrounding the fiber.