All-dielectric metasurface for optical focusing

We propose the design of a dielectric flat lens for visible wavelengths, capable of efficiently focus the incident field at a given distance. Our approach relies on the recently proposed exploitation of high-index dielectric resonators with spectrally overlapping electric and magnetic dipole resonances of equal strength. This allows the design of "metasurfaces" characterized by a nearly-full transmission and phase coverage of 360 degrees. Our numerical results confirm that this type of lenses is capable to manipulate and efficiently focus light with low absorption losses. Furthermore it is directly integrable into a nanophotonic system, thanks to its low profile compared to traditional lenses.