Liquid Crystal Devices for the Reconfigurable Generation of Optical Vortices

We present two liquid crystal devices specifically designed to dynamically generate optical vortices. Two different electrode geometrical shapes have been lithographically patterned into vertical-aligned liquid crystal cells. First, we demonstrate a pie-shape structure with 12 slices, which can be adjusted to produce spiral phase plates (SPP) that generate optical vortices. Moreover, the same device can be used to generate a pseudo-radially polarized beam, by simply adding two quarter-wave plates on each side. A second device has been fabricated with spiral shaped electrodes, which result from the combination of a SPP with the phase of a diffractive lens. This device acts as a spiral diffractive lens (SDL), thus avoiding the requirement of any additional physical external lens to provide focusing of the generated optical vortices. In both devices, the phase modulation can be adjusted by means of the voltage applied to the patterned electrodes, in order to change the properties of the generated optical vortex beams. Experimental demonstrations are provided for different wavelengths.