Generation of achromatic auto-focusing Airy beam for visible light by an all-dielectric metasurface

The focusing performance of optical beams has always played an important role in various applications such as imaging, displaying, and sensing. In contrast to a traditional focused beam with gradually increasing light intensity, an auto-focusing Airy beam exhibits an abrupt way of focusing light energy. However, owning to the chromatic dispersion of light, the previously demonstrated auto-focusing Airy beam always suffers from chromatic aberration. Here, we show that with judicious dispersion engineering of its constituent nanostructures, a metasurface can generate auto-focusing Airy beam without chromatism for the visible light. In experimental demonstration, we implement a dielectric metasurface composed of TiO2 nanopillars that generates an achromatic auto-focusing Airy beam with diffraction-limited performance covering the wavelength range from 450 to 600 nm. This study paves the way toward efficient achromatic auto-focusing Airy beam generation based on flat optical components, enabling diverse potential applications including biomedical imaging, light-sheet microscopy, and particle manipulation.