Figure 1.

Scanning Electron Micrograph of Metalenses Classified by Phase Modulation Types

(A) Plasmonic resonant type metalens that compensates for phase by using controlled aspect ratio and two resonant wavelengths of gold nanorods. Reprinted with permission from (Wang et al., 2017b). Copyright 2017, Springer Nature.

(B) Geometric phase type of metalens in which phase shift is achieved by rotation of silicon nanofins by systematically increasing angles. Reprinted with permission from (Khorasaninejad et al., 2016a). Copyright 2016, American Chemical Society.

(C) Propagation phase type metalens in which the effective index is adjusted to reach the required phase profile by modifying the diameters of TiO₂ nanopillar according to the position. Reprinted with permission from (Khorasaninejad et al., 2016b). Copyright 2016, American Chemical Society.