Author(s): Jonathan Leach, Eric Yao and Miles J Padgett


“An optical beam with an eilΦ phase structure carries an orbital angular momentum of lħ per photon. For integer l values, the phase fronts of such beams form perfect helices with a single screw-phase dislocation, or vortex, on the beam axis. For non-integer l values, Berry (2004 J. Opt. A: Pure Appl. Opt. 6 259) predicts a complex-phase structure comprising many vortices at differing positions within the beam cross-section. Using a spatial light modulator we produce eilΦ beams with varying l. We examine the phase structure of such beams after propagation through an interference-based phase-measurement technique. As predicted, we observe that for half-integer l values, a line of alternating charge vortices is formed near the radial dislocation. ”

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Publication:New Journal of Physics
Issue/Year: New J. Phys. 6 (2004) 71,
DOI: 10.1088/1367-2630/6/1/071