Geometric phase metasurfaces for linearly polarized light

Abstract

The geometric phase is a universal concept in modern physics and has enabled the development of metasurfaces for versatile wavefront shaping. However, its realization in metasurfaces has been restricted to circularly polarized light, confining geometric phase metasurfaces to helicity-dependent operation and excluding them from the linear-polarization domain that dominates modern optics. In this work, we overcome this limitation by harnessing exceptional points of non-Hermitian physics. We introduce and experimentally realize quasi-exceptional-point metasurfaces that exploit engineered singularities to directly impart a geometric phase onto linearly polarized light. Proof-of-principle demonstrations with gratings and holograms confirm broadband and high-fidelity wavefront shaping across arbitrary linear polarizations, which has not been achieved with previous phase modulation approaches. By revealing an intrinsic connection between geometric phase and non-Hermitian photonics, our work resolves a long-standing theoretical impasse and establishes a new framework for high-dimensional light control, opening opportunities for scalable polarization optics, advanced imaging, holography, optical communications, and integrated photonics.