Ordered Polar Topological Domains Enabling Giant Second‐Harmonic Generation in Ferroelectric Nematic Liquid Crystals

Abstract

ABSTRACT Developing high‐performance nonlinear optical materials that simultaneously deliver large effective nonlinearity and device‐level integrability remains a longstanding challenge. Ferroelectric nematic liquid crystals (FNLC) have emerged as a promising platform owing to their intrinsic non‐centrosymmetry, theoretically predicted large second‐order nonlinearity, and solution processability on diverse substrates. However, realizing strong second‐harmonic generation (SHG) in FNLCs has been hindered by pronounced orientational disorder inherent to fluidic systems without lattice constraints. Here, this limitation is overcome through a surface‐anchoring strategy that induces highly ordered polar topological structures within self‐assembled FNLC droplets. The resulting architecture yields a giant effective SHG coefficient of 56.9 pm/V—an order of magnitude higher than previously reported FNLC systems—together with SHG efficiency surpassing that of benchmark LiNbO 3 films of comparable thickness. Moreover, the system exhibits broadband SHG response, while the engineered polar topology enables passive, field‐free spatial optical modulation with a contrast ratio of 330%. The combination of giant nonlinearity, outstanding SHG efficiency, broadband SHG response, spatial optical modulation, and solution processability establishes a new paradigm for integrated nonlinear photonic devices.