Optical microtraps for cold atoms based on near-field diffraction

Full text: In recent years there has been significant interest in studies on the development of neutral atom traps and the applications thereof. One novel approach to the development of miniature atom traps involves the optical near-fields formed by laser diffraction on an array of circular apertures in a thin screen. This approach can be adapted in order to fabricate an array of atom microtraps and, accordingly, produce a large number of trapped atomic microensembles from a single initial atomic cloud or beam. In this paper, we propose and analyze such near-field Fresnel-type atom microtraps with a characteristic aperture size approximately equal to the optical wavelength incident on the thin screen. Our analysis of the atom microtraps shows that, for a moderate laser intensity of about 10 W/cm2, the traps can store atoms with a kinetic energy equivalent to ∼ 100 μK, and with estimated lifetimes of ∼ 1 second. Our analysis for 85Rb and 133Cs atoms shows that the potential well depth of the micro-traps is mainly determined by the intensity of the incident laser field and the detuning. By varying these two parameters one can achieve robust control over the trap parameters. The incident laser intensity of 10 W/cm2 corresponds to about 0.5 μW of laser power incident on each individual aperture. With such trap parameters one can perform atom optics experiments by blending microfabrication technology with cold atoms for site selective addressing of microtraps. (author)