All Optical 3-D Trapping through a Single-Fiber Tweezer

The authors present a new, simple and low-cost, approach that allows obtaining an all optical 3-D single-fiber tweezers. The above mentioned limitations are overcome by using an annular core fiber (or a multifiber system characterised by an annular distribution of the cores) and by properly shaping the fiber-end, as a truncated cone. Exploiting the total reflection at the interface between the fiber and the surrounding medium, beam convergence at considerable distance from the fiber end and with high numerical aperture is achieved.