Liquid crystal polymer optical vortex phase masks for ultraviolet 1 wavelengths

Liquid crystal materials for making vector vortex waveplates for ultraviolet wavelengths have been investigated. Both an appropriate alignment material and a polymerizable liquid crystal monomer that is stable in thin layers have been found. These materials were used to manufacture both uniform half-wave plates and vector vortex waveplates for ultraviolet wavelengths. A laser line focus was used to write the vortex waveplates on a rotating substate. We describe two of our fabricated monochromatic vector vortex waveplates with measured half-wave wavelengths of 353 nm and 325 nm. These waveplates show good geometric vortex patterns all the way down to central defect regions as small as 2.2 microns. While these initial masks were designed for single wavelength operation in order to first investigate materials and establish fabrication feasibility, it should next be possible to make broadband ultraviolet vortex masks using familiar multilayer techniques. Such broadband ultraviolet vortex masks could be of interest for coronagraphic exoplanet observations at ultraviolet wavelengths.