Electrostatic Reconfiguration of Photo‐Patterned Periodic Structures With Half‐Integer Twist Disclination Lines in Ferroelectric Nematic Liquid Crystals

The recently discovered ferroelectric nematic liquid crystals, combining fluidity with spontaneous polarization, offer unique opportunities for engineering polar domain structures for (nonlinear) photonic applications. A central challenge lies in achieving precise control over the self‐assembly of their polar order in confined geometries. This control is demonstrated through photoalignment patterning, which creates periodic arrays of half‐integer twist disclination lines. In RM734, the nematic to ferroelectric nematic (N F ) phase transition induces spontaneous structural reconfiguration with disclination line displacement. Because of the broken inversion symmetry in the N F phase, the resulting half‐integer disclinations template periodic localized polarization reversal mediated through surface‐pinned defects or polarization reversal walls. Polarized optical microscopy combined with optical simulations reveals the self‐assembled bulk director configuration in both phases. Contrasting experiments with and without ionic dopants emphasize the important role of electrostatic self‐energy in determining the self‐assembled configuration. Different N F materials and geometric parameters influence structural formation, leading to diverse structures including polar 2‐twist disclination lines separating domains with opposite twist handedness. This research provides new insights into ferroelectric nematic self‐assembly for next‐generation (nonlinear) photonic devices.