Quasi 3-dimensional optical trapping by two counter-propagating beams in nano-fiber.

Optical forces on a nanoparticle around an absorptive dielectric nano-fiber illuminated by two linear polarized counter-propagating beams were investigated. The results show the scattering force of the two beams causes the steady trapping along the fiber and the gradient force makes the trapping in the transverse plane of the nano-fiber. By altering the intensity ratio between the two incident beams and the polarization direction of the beams, manipulation along the nano-fiber and in the transverse direction can be realized, respectively. The numerical results present a new promising method to realize quasi 3-dimensional optical manipulation.