Abstract
Surface topography and refractive index profile dictate the
deterministic functionality of a lens. The polarity of most lenses reported so
far, that is, either positive (convex) or negative (concave), depends on the
curvatures of the interfaces. Here we experimentally demonstrate a
counter-intuitive dual-polarity flat lens based on helicity-dependent phase
discontinuities for circularly polarized light. Specifically, by controlling
the helicity of the input light, the positive and negative polarity are
interchangeable in one identical flat lens. Helicity-controllable real and
virtual focal planes, as well as magnified and demagnified imaging, are
observed on the same plasmonic lens at visible and near-infrared wavelengths.
The plasmonic metalens with dual polarity may empower advanced research and
applications in helicity-dependent focusing and imaging devices,
angular-momentum-based quantum information processing and integrated
nano-optoelectronics.