Nonlocal metasurfaces for spectrally decoupled wavefront manipulation and eye tracking.

Metasurface-based optical elements typically manipulate light waves by imparting space-variant changes in the amplitude and phase with a dense array of scattering nanostructures. The highly-localized and low optical-quality-factor (Q) modes of nanostructures are beneficial for wavefront-shaping as they afford quasi-local control over the electromagnetic fields. However, many emerging imaging, sensing, communication, display, and non-linear optics applications instead require flat, high-Q optical elements that provide notable energy storage and a much higher degree of spectral control over the wavefront. Here, we demonstrate high-Q, nonlocal metasurfaces with atomically-thin metasurface elements that offer notably enhanced light-matter interaction and fully-decoupled optical functions at different wavelengths. We illustrate a possible use of such a flat optic in eye tracking for eye-wear. Here, a metasurface patterned on a regular pair of eye-glasses provides an unperturbed view of the world across the visible spectrum and redirects near-infrared light to a camera to allow imaging of the eye.