Figure 2.

Polarization conversion efficiency (PCE) as a function of incident light wavelength and length (a), width (b), height (c) of the nanoblock. Horizontal dashed lines in (a–c) represent the optimized parameters (L, W, H) resulting in maximum PCE. (d) The simulated PCE of MgO nanoblock on a glass substrate as a function of wavelength. Vertical dashed lines represent the designated four different wavelengths (260 nm, 300 nm, 340 nm, 380 nm) that are chosen to characterize broadband metalens properties, with a minimum PCE of 74%. The optimized structural parameters of nanoblocks are $L=180$ nm, $W=75$ nm, $H=900$ nm, and unit cell with period $\text{P}=200$ nm. (e) Calculated phase profile of nanoblocks as a function of rotation angle $\theta$ within range of 0${}^{\circ }$–180${}^{\circ }$, at the designated wavelengths.