Vector flattop beam generation for use in optical fibers

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Laser beam shaping with a uniform flattop profile has become a topic of interest in many industrial fields such as high-power beam delivery to a point of contact for laser cutting, welding and additive manufacturing. These applications require point of contact delivery through an optical fiber, hence we investigate how the flattop beam has changed (in terms of modal content and polarisation) when emerging from the fiber. These modes are not eigenmodes of free space as such they change their intensity profile as they propagate, and this may be overcome by the generation of vector flattop beams. In this research we exploit the polarisation dependence of a Spatial Light Modulator (SLM) to generate a vector flattop beam that preserves its intensity profile as it propagates. For this research we have experimental generated and simulated the vector flattop beam and the correlation between the two was found to be 86%. We propagate the vector flattop beam into a few mode step index fiber and apply a holistic classical toolkit to analyse the modal content and Stokes polarimetry of the vector flattop beam before and after propagating through the fiber.
A research report submitted in partial fulfilment of the requirements for the degree Master of Science to the Faculty of Science, School of Physics, University of the Witwatersrand, Johannesburg, 2023
Laser beam, Vector flattop