Multiple doughnut beams for trapping and dynamic manipulation of low-index microstructures

摘要

We demonstrate the use of independently controlled doughnut beams for trapping and manipulation of an array of low-index microstructures. These types of particles are generally difficult to handle using conventional optical traps due to the inverse effect of the gradient force, which repels the particles from the region of stronger light intensity. The configurable multiple doughnut beams are generated using a nearly loss-less phase-to-intensity conversion of a phase-encoded collimated coherent light source. The two-dimensional phase distribution corresponding to the optical trap pattern is encoded using a computer-programmable spatial light modulator enabling each trap to be moved arbitrarily along the transverse direction. Experiments show trapping and manipulation of hollow "air-filled" glass micro-spheres suspended in aqueous medium.