Optical fiber antenna generating spiral beam shapes

A simple method is proposed here to generate vortex beam and spiral intensity patterns from a Gaussian source. It uses a special type of optical fiber antenna of aperture similar to 80 nm having naturally grown surface curvature along its length. The antenna converts linearly polarized Gaussian beam into a beam with spiral intensity patterns. The experimentally obtained spiral patterns with single and double spiral arms manifest the orbital angular momentum, l = +/- 1, 2, carried by the output beam. Such beam can be very useful for optical tweezer, metal machining, and similar applications. (C) 2014 AIP Publishing LLC.