Use of vector polarizability to manipulate alkali-metal atoms

초록

We review a few ideas and experiments that our laboratory in Korea University has proposed and carried out to use vector polarizability li to manipulate alkali-metal atoms. li comes from spin-orbit coupling, and it produces an ac Stark shift that resembles a Zeeman shift. When a circularly polarized laser field is properly detuned between the D1 and D2 transitions, an ac Stark shift of a ground-state atom takes the form of a pure Zeeman shift. We call it analogous Zeeman effect, and experimentally demonstrated optical Stern-Gerlach effect and an optical trap that behaves exactly like a magnetic trap. By tuning polarization of a trapping beam, and thereby controlling a shift proportional to /i, we demonstrated elimination of an inhomogeneous broadening of a ground hyperfine transition in an optical trap. We call it magic polarization. We also showed significant narrowing of a Raman sideband transition at a specific well depth. A Raman sideband in an optical trap is broadened owing to anharmonicity of the trap potential, and the broadening can be eliminated by /3-induced differential ac Stark shift at a magic well depth. Finally, we proposed and experimentally demonstrated a cooling scheme that incorporated the idea of velocity-selective coherent population trapping to Raman sideband cooling to enhance cooling efficiency of the latter outside the Lamb-Dicke regime. We call it motion-selective coherent population trapping, and li is responsible for the selectivity. We include as a Supplementary Material a program file that calculates both scalar and vector polarizabilities of a given alkali-metal atom when wavelength of an applied field is specified. It also calculates depth of a potential well and photon-scattering rate of a trapped atom in a specific ground state when power, minimum spot size, and polarization of a trap beam are given.

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