Two-mode and dual-resonant planar photonic waveguides for efficient guiding and trapping of atoms

The trapping of ultra-cold atoms using two-color evanescent light waves formed by propagating modes of suspended optical rib waveguides is modeled in different configurations. Reducing the anisotropy of the two-color evanescent optical dipole potential requires two laser light components with a large frequency difference. The upper frequency is guided in the two lowest transverse waveguide modes, and the lower frequency propagates in a single-mode regime. This increases the depth of the dipole potential in the lateral direction. An additional increase in the optical dipole potential can be achieved by tuning the frequencies of the two modes to two different atomic transitions. When applied to rubidium, the total depth of the corresponding surface optical dipole traps can reach 0.3 mK or greater under reasonable conditions.