Challenging fundamental limits in the fabrication of vector vortex waveplates

Vector vortex waveplates (VVWs) are in the heart of vortex coronagraphs aimed at exoplanet detection close to bright stars. VVWs made of liquid crystal polymers (LCPs) provide structural continuity, opportunity of high order singularities, large area, and inexpensive manufacturing technology. However, to date, the performance of such devices is compromised by imperfections in singularity area that allow some residual starlight leakage. Reducing the singularity to subwavelength sizes increases the energy of elastic deformations of the LC. As a result, the azimuthally symmetric orientation pattern gives way to 3D deformations that reduce the elastic energy of the LC. The stability of radial orientation is determined by elastic constants of the LC, the thickness of the layer and the boundary conditions. In the current paper, we examin the role of those factors to determine the fundamental limits the singularity area could be reduced to for LCP VVWs.