High numerical aperture multifocal metalens based on Pancharatnam-Berry phase optical elements.

A high numerical aperture multifocal metalens was proposed based on well-designed Pancharatnam-Berry phase optical elements. Both circularly and linearly polarized incident lights could be tightly focused into diffraction-limited focal spots. Right and left circularly polarized focal spots could be realized simultaneously by illuminating a linearly polarized beam. The highest numerical aperture reached to 0.84 with full width at half-maximum of 263 nm. Moreover, we also presented a metalens whose optical elements are hybrid arranged and the metalens can realize spin-independent focusing with a numerical aperture of 0.8. The presented metalens has significant potential applications in particles manipulation and high-resolution imaging.