Polarization independent and broadband achromatic metalens in ultraviolet spectrum

Ultraviolet lenses are core components of surveillance cameras, lithography machines and UV microscopes. Traditional refractive UV lenses are bulky, expensive and easy to aging, which hinders their applications in miniaturized and integrated photonic devices. In this paper, we proposed a polarization independent, broadband achromatic metalens that consists of arrays of silicon nitride nanopillars on a flat substrate. In order to simultaneously fulfill the target phases in a wide spectrum range, the phase library is extended to 0-8π by using tall nanopillars that support high order resonances. The designed metalens has a stable focus across the entire operating wavelength range from 300 nm to 400 nm and the average focusing efficiency is as high as 50%. This polarization independent achromatic metalens can be potentially applied in compact UV cameras, UV microscopes and lithography machines. •The designed metalens has a stable focus in wavelength range of 300 to 400 nm.•The achromatic metalens is insensitive to the polarization of the incident light.•The average focusing efficiency is as high as 50%.•The focus spots are close to the diffraction limit in the entire operating wavelength range.