Two‐Step Photoalignment with High Resolution for the Alignment of Blue Phase Liquid Crystal

The self‐assembling properties of liquid crystal (LC) are ideal for realizing switchable optical components. The director organization is strongly determined by the alignment at the substrate interfaces and photoalignment is a versatile method based on linearly polarized UV light. In this work, a two‐step photoalignment procedure is proposed to pattern the alignment at the surface. Illumination with uniform polarization or with an interference pattern is combined to obtain stripe patterns or square patterns of photoalignment. It can indeed be confirmed that the nematic director follows the varying azimuthal orientation. By increasing the angle between the two interfering beams, photoalignment with sub‐micrometer resolution is obtained, compatible with the dimensions of blue phase (BP) LC unit cell. Homogeneous domains of BP II with (100) or (110) crystal orientation are obtained and their Kossel patterns are recorded. The two‐step photoalignment technique allows to create patterns with high resolution and to control the orientation of BP LC, which is promising for photonic applications that require single domains. Blue phase (BP) liquid crystals have a complex structure that is arranged in a cubic lattice, and obtaining large single‐crystalline domains is challenging. Periodic photoalignment obtained by two‐step UV laser interference allows excellent BP alignment. The period determines the size and orientation of the cubic unit cell.