Fig. 1. Schematic of dual-wavelength near- and far-field decoupling metasurfaces.

Fig. 2. (a) Structure parameters of a meta-atom. (b) Full-wave simulations varying with width and length. The colormap represents the phase given by a meta-atom. (c) Phase varying with theta for six meta-atoms at the wavelength of 1064 nm. (d) Phase varying with theta for the same six meta-atoms at the wavelength of 1550 nm. (e) Phase difference between 1064 nm and 1550 nm for six meta-atoms. (f) Cross-polarization conversion efficiency for six meta-atoms at the wavelength of 1064 nm. (g) Cross-polarization conversion efficiency for the same six meta-atoms at the wavelength of 1550 nm.

Fig. 3. (a) Meta-atom arrangement of 2 × 2 at a super-pixel. The 1 and 2 possess different structural parameters. (b) The design process of dual-wavelength near- and far-field decoupling metasurfaces. The ① represents the GS algorithm, ② represents one-to-four algorithm, and ③ represents getting structural parameters from dual-wavelength phase distribution.

Fig. 4. Simulation results. (a), (c) Near-field intensity distribution at the distance of 100 nm after the metasurface for 1064 nm and 1550 nm, respectively. (b), (d) Far-field intensity distribution after the metasurface for 1064 nm and 1550 nm, respectively.

Fig. 5. Simulation results. (a), (d) Near-field intensity distribution at the distance of 100 nm after the metasurface for 1064 nm and 1550 nm, respectively. (b), (c) Verification of the converging metalens at an incident wavelength of 1064 nm for horizontal and vertical directions, respectively. (e), (f) Verification of the converging metalens at an incident wavelength of 1550 nm for horizontal and vertical directions, respectively.

Fig. 6. Simulation results. (a) The relationships between final output focus length and initial input focus length. (b) The average efficiency of focusing obtained for 1064 nm and 1550 nm. (c), (d) The FWHMs obtained for horizontal and vertical polarizations for 1064 nm and 1550 nm, respectively. The error bars represent the minimum and maximum values.