Dynamic Control of Phase Matching in Nonlinear Metasurfaces Using Pancharatnam–Berry Phase

ABSTRACT Reconfiguring the spectral output of nonlinear metasurfaces after fabrication remains challenging. We address this by exploiting the nonlinear Pancharatnam–Berry phase of ‐symmetric plasmonic metasurfaces. By integrating two metasurfaces inside a multipass cell, we experimentally demonstrate continuous spectral tuning of second‐harmonic generation (SHG) phase‐matching peaks across a 900–970 nm pump range by rotating one metasurface relative to the other. The extracted geometric phase follows the dependence, and a full tuning cycle is completed with of physical rotation. This establishes geometric‐phase metasurfaces as a reconfigurable nonlinear platform, where mechanical rotation enables post‐fabrication and broadband tuning of nonlinear optical responses.