Abstract

Using a photoalignment technique with a sulphonic azo-dye as the surfactant aligning material, we fabricated electrically tunable liquid crystal q-plates with topological charge 0.5, 1.5 and 3 for generating optical vortex beams with definite orbital angular momentum (OAM) 1,3 and 6 per photon (in units of h), respectively.We carried out several tests on our q-plates, including OAM tomography, finding excellent performances.These devices can have useful applications in general and quantum optics.