Optics and Photonics Society of Iran

Propagation of a plane wave having a special polarization state through a phase plate with a spatially variable pattern of anisotropy leads to a vortex beam generation. The polarization singularity can be created with a specified pattern of liquid crystal molecules on a phase plate. Such a device contains so characteristics named q-plate (QP). In this work, we introduce an experimental method for fabrication of an electrically tunable QP with parameter q=1 in which liquid crystal molecules aligned in the azimuthal direction. By applying a suitable AC voltage on the device, we achieve to the desired value of birefringence and as a result the incident beam having a Gaussian intensity profile changed to a beam of a profile with symmetric doughnut shape. Wave-front slopes were measured with a two channel wave-front sensor based on moiré deflectometry. The result demonstrates that the wave-front of the passing beam has vortex shape with topological charge of equal to 2.