Rotationally invariant ring-shaped liquid crystal structures between two substrates with different photoalignment

Planar patterned photoalignment can be used to align liquid crystals (LCs) in any azimuthal orientation. Using different patterns on both substrates, we fabricated and analyzed complex three-dimensional LC structures. We developed four configurations in which planar patterns with rotational symmetry are defined at each substrate. All four configurations generate a ring-shaped region in the bulk of the sample where the LC aligns vertically. The director configurations are calculated using numerical simulations and are verified by comparing the simulated optical transmission to the measured microscopy images. The vertical alignment in the bulk of the cell makes it possible to use this configuration as a waveguide, as demonstrated by a waveguide mode simulation.