Abstract
We propose several schemes to realize a tractor beam effect for ultracold atoms in the vicinity of a few-mode nanowaveguide. Atoms trapped near the waveguide are transported in a direction opposite to the guided mode propagation direction. We analyse three specific examples for ultracold 23Na atoms trapped near a specific nanowaveguide (i.e. an optical nanofibre): (i) a conveyor belt-type tractor beam effect, (ii) an accelerator tractor beam effect, and (iii) a quantum coherent tractor beam effect, all of which can effectively pull atoms along the nanofibre toward the light source. This technique provides a new tool for controlling the motion of particles near nanowaveguides with potential applications in the study of particle transport and binding as well as atom interferometry.
Highlights
Optical tractor beams, where light incident from a single direction causes particles to move against the light propagation direction and towards the beam source, are an intriguing example of science fiction[1] inspiring the creation of a scientific technology
The tools required to realize scheme (iii) for atoms trapped near an optical nanofibre are the same as for scheme (ii), and our calculations demonstrate that the required optical potential can be achieved within typical experimental parameters
Regarding assumptions (a) and (b) in scheme (iii), in order for the quantum coherent scheme to transport atoms efficiently, the atoms must have a small initial momentum spread along the z axis relative to the lattice momentum spacing ħkeff
Summary
Optical tractor beams, where light incident from a single direction causes particles to move against the light propagation direction and towards the beam source, are an intriguing example of science fiction[1] inspiring the creation of a scientific technology. We note that for co-propagating waves, the condition ω1 =ω2 is not trivial to satisfy in free space when k1 and k2 differ At this point, the advantage of using few-mode nanowaveguides can be seen: atoms can interact with the evanescent region of the guided modes, and a standing beat field can be generated using two copropagating modes of the waveguide. The advantage of using few-mode nanowaveguides can be seen: atoms can interact with the evanescent region of the guided modes, and a standing beat field can be generated using two copropagating modes of the waveguide It is precisely this principle which we will use to achieve a tractor beam effect. Note that on, we drop the superscript s from Ebs with the understanding that all beating fields considered in this paper will be standing beat fields of the form given in Eq 2
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