Husband, RyanEastman, JessicaHaine, Simon A.Eagle, Rhys H.Close, John D.Thomas, Ryan J.Legge, Samuel2026-07-032026-07-032040-8978ORCID:/0000-0001-9303-9307/work/219179401https://hdl.handle.net/1885/733812891We present the first rigorous experimental investigation of the propagation of Gaussian vortex beams, which are Gaussian beams imprinted with a spiral phase, under the realistic condition of an aperture-limited optical system. By combining approximate analytic results with a numerical solution of the paraxial wave equation, we produce a simple empirical model that describes the radius of the vortex singularity and its relationship with the imprinted orbital angular momentum (Formula presented) (Formula presented) and the spatial bandwidth of the optical system. We compare our empirical model with experimental data and show that we achieve excellent agreement for beams with (Formula presented) (Formula presented), 2, 5, and 10 over a range of spatial bandwidths.enPublisher Copyright: © 2026 The Author(s). Published by IOP Publishing Ltd. Original content from this work may be used under the terms of the https://creativecommons.org/licenses/by/4.0/. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.aperture-limitedGaussian vortex beamorbital angular momentumparaxial wave equation202610.1088/2040-8986/ae681e105039320571