Nonlinear geometric metasurfaces are an necessary platform for data encoding and light-field manipulation with extensive purposes in show encryption and past. Enhancing nonlinear conversion effectivity and controlling the nonlinear geometric part are equally essential for sensible use. Not too long ago, high-Q resonances in nonlocal metasurfaces have proven sturdy light-matter interactions, offering a basis for environment friendly nonlinear conversion. Nonetheless, concurrently attaining excessive effectivity and efficient part management stays a key problem. Right here, primarily based on the precept of geometric part, we effectively understand third-harmonic part management, the place the high-Q resonance corresponds to a magnetic dipole–associated quasi-BIC mode. On the ultra-narrow resonance bandwidth, the electrical area enhancement exceeds 50 instances, with high quality issue over 3000 and excessive stability underneath rotation. A 3rd-harmonic conversion effectivity of the order of 10-3 is achieved at a peak pump density of 100 MW/cm2, outperforming beforehand reported nonlinear geometric metasurfaces. This work holds important potential for on-chip nonlinear data processing and wavefront management requiring sturdy gentle–matter interplay.
