Achromatic metasurfaces: fundamental limits and some solutions

Samira Khadir

Université Cote d’Azur, CNRS, CRHEA, Rue Bernard Gregory, Sophia Antipolis 06560 Valbonne, France

Metasurface elements, based on fixed nanostructures, are inherently limited in terms of dispersion for the design of achromatic components. To design such components, a very large number of different meta-atoms is required, usually leading to the construction of complex meta-atom designs with high geometric tunability [1]. However, recent studies highlighted some fundamental limits of achromatic diffractive lenses or metalenses performances due to the limited effective refractive index range that such components can achieve [2,3].
In this work we describe a simple way of quantifying the dispersion limits of a dataset, which can be used to optimize the design of polychromatic metasurfaces. As an example, the design, fabrication and characterization of a highly effective achromatic metalens was performed using this approach. Moreover, we discuss another approach based on the use of hybrid refractive/diffractive devices for the compensation of chromatic aberration of centimeter scale lenses.

References
1. Shrestha, S., Overvig, A.C., Lu, M. et al. Broadband achromatic dielectric metalenses. Light Sci Appl 7, 85 (2018)
2. Engelberg, J. and Levy, U., Achromatic flat lens performance limits, Optica 8, 834-845 (2021)
3. Presutti, F. and Monticone,F., Focusing on bandwidth: achromatic metalens limits, Optica 7, 624-631 (2020)