Broadband Achromatic Metasurface-Refractive Optics

Abstract

Existing\nmethods of correcting for chromatic aberrations in optical\nsystems are limited to two approaches: varying the material dispersion\nin refractive lenses or incorporating grating dispersion via diffractive\noptical elements. Recently, single-layer broadband achromatic metasurface\nlenses have been demonstrated but are limited to diameters on the\norder of 100 μm due to the large required group delays.\nHere, we circumvent this limitation and design a metacorrector by combining a\ntunable phase and artificial dispersion to correct spherical and chromatic\naberrations in a large spherical plano-convex lens. The tunability\nresults from a variation in light confinement in sub-wavelength\nwaveguides by locally tailoring the effective refractive index. The\neffectiveness of this approach is further validated by designing a\nmetacorrector, which greatly increases the bandwidth of a state-of-the-art\nimmersion objective (composed of 14 lenses and 7 types of glasses)\nfrom violet to near-infrared wavelengths. This concept of hybrid metasurface-refractive\noptics combines the advantages of both technologies in terms of size,\nscalability, complexity, and functionality.