Siemens-Westinghouse Competition.pdf

Creation of Optical Vortices Using an Adjustable Spiral Phase Plate and Computer-Generated Holograms Physics Individual Project Siemens-Westinghouse Competition October 2005 Amol Jain Herricks High School New Hyde Park, New York 11040 and Laser Teaching Center Stony Brook University Abstract An adjustable spiral phase plate and computer-generated holograms were inves- tigated as methods for creating optical vortices. The phase plate was created by cutting a plastic microscope cover slip from a corner to its center and separat- ing the resultant tabs by inserting a uniformly thick wedge between them. The computer-generated holograms were designed by mathematically interfering an oblique plane wave with an optical vortex in Matlab; we then printed them on common overhead transparencies. The two devices were tested in an originally developed interferometer, and the intensity profiles of vortices created by shining a laser beam through the phase plate and CGHs were measured. The curvature of the phase plate was mapped using an optical scanning setup. A composite-vortex grid hologram was designed for future use in an orbital angular momentum sorter in conjunction with the spiral phase plate. Both devices simplified previous designs and proved to be a highly effective means of generating optical vortices. 1 1 Introduction Vortices are a ubiquitous phenomenon in nature. They have long been observed in hurricanes, tornadoes, and even something as simple as the swirl of coffee in a mug. It was only in 1974, however, that Berry and Nye first put forth the theory that a light field could assume the character of a vortex [1]. Since then, optical vortices have become more than a mathematical curiosity and have proved their practical value in numerous fields, including optical tweezing and quantum computation [2]. An optical vortex beam is characterized by a doughnut-shaped intensity distribution with a phase singularity, and hence zero field amplitude, at the center. Optical vor