Observation of the full spiral spectrum of a light beam with single-pixel detection

Abstract

We demonstrate experimentally a simple and easy-to-use technique aimed at measuring the complex orbital angular momentum spectrum of an arbitrary optical field making use of just polarization measurements. The technique can be applied to any other family of modes used to describe the spatial shape of optical beams. The idea is inspired by a formal analogy that exists between classical fields that can show a certain amount of correlations between different degrees of freedom (polarization and spatial shape) and the degree of entanglement that might exist between two subsystems, so it is an example of a quantum-inspired classical technology.