Vortex Propagation in Orbital Angular Momentum Beams and the Effects of a Limited Aperture

TL;DR

This paper investigates how optical vortices generated with orbital angular momentum behave when passing through limited apertures, revealing complex propagation dynamics that depend on the orbital phase and system bandwidth.

Contribution

It introduces a numerical model for vortex propagation in aperture-limited systems and compares it with experimental data, highlighting the non-trivial effects of apertures on vortex evolution.

Findings

Numerical model accurately predicts vortex development in near field.

Aperture size significantly influences vortex propagation dynamics.

Agreement between model and experiment confirmed for multiple orbital angular momentum values.

Abstract

When generating light with orbital angular momentum by imprinting orbital phase onto a standard Gaussian beam, it is often assumed that the propagation of the generated spatial mode is a Laguerre-Gaussian. However, the true propagation of this beam in a realistic, aperture-limited optical system is non-trivial and has not been thoroughly explored in existing literature. We explore a numerical model that shows the development of an optical vortex mode, propagating from the plane of phase modulation, and the relation of these dynamics to the orbital phase factor $\ell$ and the spatial bandwidth of the optical system. The results of this model are compared to experimental data for beams with $\ell$ values 1, 2, 5, and 10 propagating through a range of spatial filters, with the described model showing agreement in the near field regime.