Laser nanotraps and nanotweezers for cold atoms: 3D gradient dipole   force trap in the vicinity of Scanning Near-field Optical Microscope tip
  Using a two-dipole model of an optical near-field of Scanning Near-field Optical Microscope tip, i. e. taking into account contributions of magnetic and electric dipoles, we propose and analyze a new type of 3D optical nanotrap found for certain relations between electric and magnetic dipoles. Electric field attains a minimum value in vacuum in the vicinity of the tip and hence such a trap is quite suitable for manipulations with cold atoms. 
V.V.Klimov, S. K. Sekatskii and G. Dietler