Silicon-based super-resolution metalens with weak sidelobe

Metasurface is a spatially varying ultrathin nanostructure that has been widely studied and used in optical super-resolution focusing, either in lenses or in systems. However, with the decrease of the focal spot size of the metalens, large sidelobes are inevitably generated, limiting the field of view and potential applications of the lens. In this paper, a method for producing super-resolution metalens with a large numerical aperture (NA=0.944) and weak sidelobe is presented. For a circularly polarized light with the wavelength of λ=632.8 nm, a super-resolution point-focusing with a weak sidelobe is realized based on PB phase regulation of silica-based metasurface. Experimental results show that the FWHM (full-width at half maximum) of our focusing spot is 0.45λ, which is less than the diffraction limit of 0.53λ (the diffraction limit is 0.5λ/NA), and the sidelobe ratio (SR) is 0.07. Our proposed super-resolution metalens bears the potential to realize the miniaturization, lightweight and integration of super-resolution optical devices or systems.