Digitally Designed Ultrathin Metasurfaces for Multiwavelength Optics in the Visible

Metasurface-based optical elements have the ability to shape wavefronts by locally changing the properties of the incident illumination. They hold great potential to promote a new generation of wearable devices and thin optical systems for imaging and sensing. However, due to the diffractive nature of these metasurfaces, their performance is highly sensitive to the wavelength of operation. In this paper, we present a new approach to design single-layer multi-wavelength metasurfaces using ultrathin dielectric resonators (thickness
$<<$
wavelength) as structural elements. The electromagnetic response of these resonators can be tailored and used to manipulate the transmitted light. We introduce a digital transmission modulation scheme which enables opportunities to design novel multi-wavelength optics beyond conventional binary diffractive optics. The potential of the proposed approach is demonstrated with achromatic meta-lenses in the visible band, one of the most challenging functionalities to achieve with a single-layer flat optical element.