Slanted Lithium Niobate Meta‐Atoms Enable Nonlinear Chiroptical Response With Electro‐Optic Tunability

ABSTRACT Chiral metaphotonics offers a powerful route to boost intrinsically weak optical activity, yet the dynamic control of nonlinear chiroptical responses remains a formidable challenge. Here, we propose and experimentally demonstrate a facile symmetry‐breaking strategy for constructing nonlinear chiral metasurfaces on a lithium niobate‐on‐insulator (LNOI) platform. By simply slanting square‐pillar meta‐atoms along two orthogonal axes, all mirror symmetries are simultaneously broken, yielding a quasi‐three‐dimensional architecture with pronounced intrinsic chirality at both fundamental and second‐harmonic (SH) wavelengths. This design eliminates the need for complex multi‐step nanofabrication and exhibits high tolerance to fabrication imperfections. Experimentally, the fabricated metasurface displays a distinct linear circular dichroism (CD) and a markedly enhanced nonlinear CD, confirming the superior chiral sensitivity of nonlinear processes. Crucially, by harnessing the strong Pockels effect of LN, we achieve active electro‐optic modulation of the nonlinear CD with low driving voltages. This demonstration of electrically tunable nonlinear chirality establishes LN as a versatile platform for dynamic chiral nanophotonics and paves the way toward switchable nonlinear light sources, tunable chiral holography, and reconfigurable nonlinear information processing.