Scalar vortex beams may be generated using multiple techniques. However, the generation of vector vortex beams from a single optical component has fewer options. A liquid crystal plate called a q-plate has a distribution of optical axis alignments that can vary radially and azimuthally. These plates provide a very robust and cost-effective method of generating vector-vortex and structured beams based on the Pancharatnam-Berry phase. Multi-plate gadgets can be generated from these plates to generate full-Poincaré beams, wavelength-tunable q-plates, and a wide range of structured light. The successful realization of such gadgets relies on the careful characterization of individual plates, which are characterized by their topological charge, offset angle, and retardance at the designed wavelength. In order to make complex multi-plate devices, a thorough mathematical modeling followed by multiple experimental measurements and simulations is essential. In the present work, a systematic and thorough protocol for such a characterization is provided with ample experimental and simulation results. The results presented here should be of value to experimentalists and device makers alike.
Rajput et al. (Tue,) studied this question.