Generation, Topological Charge, and Orbital Angular Momentum of Off-Axis Double Vortex Beams

Abstract

Compared with the on-axis vortex beam and the off-axis single vortex beam, the off-axis double vortex beam has more control degrees of freedom and brings rich physical properties. In this work, we investigate theoretically and experimentally the generation, topological charge (TC), and orbital angular momentum (OAM) of off-axis double vortex beams. It is demonstrated that the tilted lens method can detect not only the magnitudes and signs of two TCs of the off-axis double vortex beam but also the spatial distribution of the TCs. Moreover, the average OAM value of the off-axis double vortex beam decreases nonlinearly as the off-axis distance increases, although its TC is independent of the off-axis distance of phase singularities. The results indicate that the average OAM of the off-axis double vortex beam can be easily controlled by changing the relative position of two-phase singularities, thereby realizing the applications of multi-degrees of freedom particle manipulation, optical communication, and material processing.