Figure 3.

(a–d) Simulated normalized intensity profiles of focal spot at $y=0$ ($x-z$ plane) for simple metalens at the designated wavelengths ${\lambda }_d=260,300,340,380\text{nm}$ respectively. (e–h) Simulated normalized focal spot intensity profiles at $z=f$ ($x-y$ plane) for the corresponding wavelength. (i–l) Normalized intensity profiles of focal spots presented at (e–f) along the dashed horizontal cut (at $y=0$) for the corresponding wavelength. The profiles present full width at half maximum of $182,204,223,240\text{nm}$ respectively. Each metalens is illuminated by monochrome RCP incident light. All the metalenses have $20\mathrm{\mu }$m diameter, and the numerical aperture is calculated as (NA$\approx 0.8$) at each wavelength.