Tunable atom-trapping based on a plasmonic chiral metamaterial

Chiral metamaterials provide a very convenient way to actively regulate the light field via external means, which is very important in nanophotonics. However, the very weak chiral response of a generally planar metamaterial severely limits its application. Therefore, it is important to design a system with large circular dichroism. Here we report an optical metamaterial with strong chirality in a bilayer gear-shaped plasmonic structure and consider this chiral response of such fields on tunable atom (⁸⁷Rb) trapping. Simulation results show that maximum chiral response is observed when the two layers of the gear-shaped structures are rotated from each other by an angle of 60° at λ = 760 nm. Also, we demonstrate an active tunable potential for three-dimensional stable atom-trapping with tunable range of position and potential of a neutral atom of ~58 nm and ~1.3N mK (N denotes the input power with unit mW), respectively. In addition, the trap centers are about hundreds of nanometers away from the structure surface, which ensures the stability of the trapping system. The regulation of neutral atom trapping broadens the application of chiral metamaterials and has potential significance in the manipulation of cold atoms.