Polarization-dependent distortion of the vortex light field generated using a vortex retarder

A vortex retarder (VR) is a widely-used optical component for converting Gaussian light beams into vortex beams, exhibiting unique advantages in a few broadband applications. However, the quality of the vortex beam generated using a VR-based system is highly dependent on the polarization state of the incident light. In this letter, we investigate both theoretically and experimentally the distortion of the output vortex light field resulting from the misalignment of the light polarization state in a VR-based vortex-beam-generation system. While a theoretical model was constructed to study the optical properties of the generated vortex beams at different polarization states of the incident Gaussian beams, systematic characterizations on near- and far-field profiles of the vortex light fields were performed in the experiment. The results exhibit that non-ideal circularly-polarized incident light can introduce a sinusoidal-shape modulation on the optical field, resulting in both phase and intensity distortions of the generated vortex light beam. Our findings provide some insights into the generation and propagation processes of vortex light fields, which could be useful for the practical construction of a VR-based vortex-beam generation system.