Broadband Achromatic Metalens in the Midinfrared Range

A broadband metamaterial lens that does not suffer from chromatic aberration is of particular interest for optical applications at midinfrared frequencies. Due to the intrinsic dispersion of the building blocks, though, such a broadband achromatic metalens has remained elusive. The authors use the Pancharatnam-Berry phase and propagation phase to control the wave front of light, from which the chromatic aberration can be eliminated effectively. This result points the way to practical midinfrared devices, $e.g.$ for communication technology.