Fig. 1. Schematic diagram of principle of achromatic metalens. (a) Metalens focusing; (b) phase distribution of a metalens

Fig. 2. Simulation results of unit structure. (a) Schematic diagrams of unit structure of metalens; (b) phase response of each unit structure at different incident wavelengths; (c) transmittance of each unit structure at different incident wavelengths; (d) normalized magnetic field energy distributions with L=380 nm and W=170 nm at different incident wavelengths

Fig. 3. Field strength distributions of metalenses. (a) Normalized simulated intensity distributions in x-z plane; (b) normalized focus spot effect diagrams in x-y plane; (c) focal field normalized intensity along x-axis; (d) SR parameter curve

Fig. 4. Focusing characteristics of metalens at different wavelengths. (a) Focal lengths and FWHMs at different wavelengths;

Fig. 5. Normalized simulated intensity distributions of single-wavelength metalens in x-z plane