Determining the topological charge of optical vortex by intensity distribution of a quasi-Airy vortex beam

Abstract

Determining the orbital angular momentum state or the topological charge (TC) of a vortex beam is important in exploiting its applications. By analyzing the intensity distribution of the quasi-Airy vortex beam (QAVB) in far field, we find that the number of forked fringes is equal to the TCs of the vortex beam, and the direction of the forked fringes is related to the sign of TCs. Based on this property, a method of measuring the TC of optical vortex by the intensity distribution of QAVB is proposed. The range of initial topological angle (from 0 to 73°) for determining the TC of optical vortex is obtained as well as the relationship between the optimal propagation position and the initial topological angle to observe the forked fringes. In addition, the characteristics of QAVB embedded with multiple optical vortices at different locations would provide a new possibility for improving the confidentiality and the information capacity in free space optical communication.