W-T. Chen, F. Capasso
Keywords: metasurface, optics, quantum
Summary:In imaging lenses, various aberrations especially the chromatic aberration must be corrected through cascading many lenses made of different materials and curvatures. This causes imaging lenses bulky, heavy and complex. Here, we demonstrate dispersion-engineered metasurfaces, comprising only a layer of 600-nm-thick TiO2 nanostructures, capable of rendering refractive lenses achromatic and diffraction-limited across the visible spectrum. Our approach is based on compensating the glass dispersion by tailoring the group delay and group delay dispersion of each metasurface’s nanostructure. The generality of our design method can be applied to extremely complicated refractive system as well. As an example, we show a metasurface that greatly increases the achromatic bandwidth of a state-of-the-art immersion objective from the violet to near-infrared wavelengths. The objective, consisting of 14 lenses and 7 different materials, has a numerical aperture of 1.45 and is commercially available from Zeiss. Metasurface-refractive optics combines the advantages of both technologies in terms of size scalability and complexity for many applications such as imaging, augmented reality and lithography.