Generating and measuring non-diffracting vector Bessel beams

We demonstrate how to create non-diffracting vector Bessel beams by implementing a spatial light modulator (SLM) to generate scalar Bessel beams which are then converted into vector fields by the use of an azimuthally-varying birefringent plate, known as a q-plate. The orbital angular momentum (OAM) of these generated beams is measured by performing a modal decomposition on each of the beam's polarization components. This is achieved by separating the circular polarization components through a polarization grating (PG) before performing the modal decomposition. We investigate both single charged Bessel beams as well as superpositions and the results are in good agreement with theory.