Measuring the Orbital Angular Momentum of Asymmetric Light Beams by Two Cylindrical Lenses

Abstract

Here we propose and study both theoretically and experimentally two simple and high-efficiency techniques for measuring the orbital angular momentum (OAM) of paraxial laser beams. One technique relies on measuring the intensity in the Fresnel zone, averaging it over several concentric circles, and solving a set of linear equations to obtain the OAM spectrum. With the other technique, two intensity distributions are measured in the foci of two orthogonal cylindrical lenses and then first-order intensity moments are calculated. The experimental error increases from ~ 1% for small fractional OAM (up to 4) to ~ 8% for large fractional OAM (up to 30).