All Abstracts | Poster Abstracts | Talk Abstracts

Atom trapping in the evanescent field of a tapered optical fiber: towards cQED with micro-toroids and trapped atoms.

Clement Lacroute, California Institute of Technology

(Session 7 : Saturday from 9:45am-10:15am)

Abstract. Authors: C. Lacroute*, D. J. Alton*, K. S. Choi*, A. Goban*, N. P. Stern*, H. J. Kimble* *Norman Bridge Laboratory of Physics MC 12-33, California Institute of Technology, Pasadena, California 91125, USA It has recently been shown that a two-color Far Off-Resonance optical Trap (FORT) could be generated in the evanescent field of a sub-wavelength diameter optical fiber [1]. About 2000 Cs atoms were trapped 200nm away from the fiber surface, with a 50ms lifetime. This is an important result in the context of cavity Quantum Electrodynamics (cQED) with micro-resonators, where a single atom needs to be located a few hundred nanometers away from a dielectric surface to be strongly coupled to the evanescent field of a lithographically patterned waveguide [2]. The two-color FORT consists of the combination of a red-detuned attractive potential and a blue-detuned repulsive potential [1]. The two trapping beams propagate in a sub-wavelength optical fiber, and the resulting evanescent-field potential confines the atoms radially at a distance of a few hundred nanometers from the fiber surface. Azimuthal confinement can be obtained by a right choice of relative polarizations of the trapping beams. Adding a counter-propagating red-detuned beam provides longitudinal confinement by generating a standing wave. We investigate the evanescent electric field and its polarization in the vicinity of the fiber surface, which is found to be spatially varying in all directions on the optical wavelength scale, and is not everywhere linear because of the out-of-phase, non-vanishing longitudinal component of the electric field. Elliptically polarized light can result in a splitting of the atomic Zeeman sub-levels by a so-called fictitious magnetic field [3]. We quantify this splitting for the use of a pair of "magic wavelength" trapping beams that minimize the spread in the atomic polarizabilities for both red and blue detuned light fields [4, 5], and the subsequent spread of the total trapping potential. We will discuss experimental consequences in terms of lifetime and coherence times of the trapped atoms, and the implementation of such a fiber trap in a cQED experiment using micro-toroids. This work is supported by NSF, NSSEFF, DARPA, and the Northrop Grumman Corporation. [1] Vetsch et al., PRL 104(20), pp. 203603 (2010). [2] Aoki et al., Nature 443(12), pp. 671-674 (2006). [3] I. Deutsch and P.S. Jensen, PRA 57(3), pp. 1972-1986 (1998). [4] McKeever et al., PRL 90(13), pp. 133602 (2003). [5] Kien et al., J. Phys. Soc. Jpn. 74, pp. 910-917 (2005).