A tunable liquid crystal polarization converter based on hybrid alignment with a deeply rubbed polyimide surface

This work demonstrates a tunable liquid crystal polarization converter (LCPC) constructed using two conductive glass substrates that are treated with homogeneous alignment and azimuthal alignment, respectively. The azimuthal alignment surface is deeply rubbed to enhance the alignment performance to tilted LC molecules compared with the homogeneous alignment surface. The LC layer initially presents twisted-azimuthal texture, which is capable of converting linear polarization to azimuthal (radial) polarization when the polarization direction of incident light is set parallel (perpendicular) to the homogenously aligned LC directors. If the LC molecules are tilted in an electric field, the tilted LC molecules will be realigned by the azimuthal alignment surface with deep rubbing grooves and present azimuthal texture, which can convert linear polarization to axial polarization. Additionally, increasing the voltage enables the LC molecules to reorientate along the electric field and lose converting effect, and such an operation can switch off the LCPC.