On-axis complex-amplitude modulation for the generation of super-stable vector modes

We propose a technique to generate complex vector beams with high quality and stability. Our approach relies on the combination of complex amplitude modulation (CAM) and on-axis modulation, two techniques that seem incompatible at first glance. The first one produces scalar structured light fields in phase and amplitude with high accuracy, while the second one is preferred for generating vector beams of great stability although of reduced quality. Specifically, the idea behind our technique is to send the shaped light produced by CAM co-axially with the zeroth order, rather than diffracted to the first order, as it is commonly done. We first describe our technique, explaining the generation of the hologram and experimental setup to isolate the desired vector mode, and then present experimental results that corroborate our approach. We first address the quality of the generated beams using Stokes polarimetry to reconstruct their transverse polarisation distribution, and then compare their stability against the same mode produced using a Sagnac interferometric method. Our vector beams are of good quality and remarkably stable, two qualities that we expect will appeal to the community working with vector modes.