Experimental and theoretical study of the single-beam optical fiber trap

We have developed an optical fiber trapping system and verified that micro-sphere could be trapped and manipulated by a weakly focused single laser beam emerging from an optical fiber end which was inserted into a sample chamber at an angle of 35 degree. In this paper, axial and transverse trapping forces exerted on a micro-sphere were experimentally and theoretically analyzed to corroborate the single-beam optical trap using an optical fiber. Experimental results were shown to be in excellent agreement with a numerical model that predicted the axial and transverse trapping efficiencies. From these results, it was found that the vector sum of axial and transverse forces acting on a sphere gave a restoring force directed back to the stable point, and transverse force played a significant role in trapping and manipulation of a micro-sized object by means of an optical fiber. Furthermore, we experimentally verified that our proposed single-beam fiber optic trapping system was most economical, much simpler to operate, and required relatively low optical power to capture particle as compared with other embodiments.