Active control of phase matching in nonlinear metasurfaces using Pancharatnam--Berry phase

TL;DR

This paper demonstrates a method to reconfigure the spectral output of nonlinear metasurfaces post-fabrication by mechanically rotating metasurfaces to achieve broadband spectral tuning of second-harmonic generation.

Contribution

The work introduces a reconfigurable nonlinear metasurface platform utilizing the nonlinear Pancharatnam--Berry phase for broadband spectral tuning via mechanical rotation.

Findings

Achieved continuous spectral tuning of SHG peaks across 900--970 nm.

The geometric phase follows a $3\sigma\theta$ dependence, completing a $2\pi$ cycle with 120° rotation.

Mechanical rotation enables post-fabrication, broadband tuning of nonlinear optical responses.

Abstract

Reconfiguring the spectral output of nonlinear metasurfaces after fabrication remains challenging. We address this by exploiting the nonlinear Pancharatnam--Berry phase of $C_{3v}$-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 $3\sigma\theta$ dependence, and a full $2\pi$ tuning cycle is completed with $120^{\circ}$ 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.