Gradient force pattern of truncated hyperbolic-cosine-Gaussian beam through phase plate focusing system

Abstract

The evolution of the gradient force pattern of hyperbolic-cosine-Gaussian beams induced by a three-zone pure phase plate is numerically investigated. The pure phase plate consists of three concentric zones—the center circular zone, the inner annular zone—and the outer annular zone and the phase variance of inner annular zone is adjustable. The results show that the proposed plate may induce tunable gradient force on the particles in the focal region. The optical trap shape is obviously tunable and multiple traps may occur with changing geometrical parameters of the phase plate. An optical trap shift can be induced by changing the phase variance of the inner annular zone portion. The phase plate may be a very promising method of transporting trapped particles and can be used to construct controllable optical tweezers.