Figure 1.

Design of the metalens. (a) Schematic of the metalens and its building block, the ${\mathrm{Si}}_3{\mathrm{N}}_4$ nanorod. (b) Si₃N₄ nanorod on SiO₂ substrate. (c) and (d) side and top views of the unit cell showing the height, width, and length of the nanorod having unit cell dimensions S × S. (e) By the rotation of the nanorod, the required phase is imparted by an angle of $\mathsf{\theta }$ following the geometric Panchratnam–Berry phase.