Magnetooptical force in the resonance field formed by elliptically polarized light waves
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Magnetooptical Force in the Resonance Field Formed by Elliptically Polarized Light Waves O. N. Prudnikova, b, A. V. Taœchenacheva, b, A. M. Tumaœkina, b, and V. I. Yudina, b a
Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090 Russia
b Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, pr. Lavrent’eva 13/3, Novosibirsk, 630090 Russia
e-mail: [email protected] Received October 17, 2007
Abstract—The dependence of the magnetooptical force on the ellipticity of the polarization of light beams is studied in terms of a one-dimensional model for closed Jg Je optical transitions. A linear velocity and magnetic-field approximation is used to find analytical expressions for the magnetooptical force for a number of transitions. In the light fields formed by waves with an elliptical polarization, qualitatively new contributions are shown to appear; they have an even dependence on the detuning of the light field and do not disappear even in the case of an exact resonance. An analysis of these results demonstrates that a magnetooptical trap can stably operate at the zero detuning of the field. Numerical methods are used to investigate the nonlinear dependence of the force on the atom velocity and the magnetic field and to estimate the characteristic atom trapping rate and the number of trapped atoms. PACS numbers: 32.60.+i, 37.10.Vz, 39.10.+j DOI: 10.1134/S1063776108050014
1. INTRODUCTION The mechanical action of a resonance laser radiation on atoms is an important field of investigation in modern atomic and laser physics. Magnetooptical traps (MOTs) of various designs make up one of the main sources of cold atoms (with a temperature of about 10– 100 µK). The useful combination of effective laser cooling and a deep magnetooptical potential (on the order of several kelvins) formed by the forces of a resonance light pressure in the presence of a nonuniform magnetic field leads to a reliable MOT operation for lenient requirements on the device parameters, such as the vacuum, the magnetic-field gradient, and the laserbeam intensity and size. The cold atoms prepared in MOTs are widely applied in various fields of physical investigations, e.g., in nonlinear ultrahigh-resolution spectroscopy, in studying atomic cooling and dynamics in optical lattices, in fundamental metrology for the creation of primary next-generation frequency standards, for achieving Bose–Einstein condensation, and so on. Like the theory of laser cooling and neutral-atom trapping [1–3], the theory of MOTs has mainly been developed for the fields formed by circularly or linearly polarized laser beams, which are usually employed in experiments. In [4, 5], we used a one-dimensional optical lattice in the absence of a magnetic field as an example and showed that the kinetics of atoms in the fields formed by elliptically polarized waves had a number of qualitative differences as compared to the cases of linear or circular polarization. For example, the use of
waves with an elliptical polarization leads to new speci
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