Ferroelectric liquid crystals with sub-wavelength helix nanostructure pitch for the generation of axial-symmetric vortex light fieldsSvetlana Kotova, Evgeny Pozhidaev, Sergey Samagin, Vladimir Kesaev and Aleksandra MayorovaEPJ Web Conf., 220 (2019) 01005DOI: https://doi.org/10.1051/epjconf/201922001005