Fig. 2

Phase modulation methods. a Symmetric and antisymmetric mode of V-shaped gold antenna. b SEM image of plasmonic resonant-phase-based metasurface. (a) and (b) are reproduced with permission [103] (Copyright 2011, American Association for the Advancement of Science). c (top) Magnetic and (bottom) electric mode of Mie-resonant-phase-based metasurface. d Field amplitude and e phase spectrum of spectrally overlapped electric dipole and magnetic dipole resonances. c-e are reproduced with permission [97] (Copyright 2015, Wiley-VCH). f Side-view SEM image of propagation-phase-based metalens (scale bar = 600 nm). Reproduced with permission [41] (Copyright 2016, American Chemical Society). g (left) Two-fold and (right) three-fold symmetric meta-atoms in a square lattice. Reproduced with permission [104] (Copyright 2021, American Physical Society). h Simulated phase shift and second harmonic generation amplitude versus rotation angle of nonlinear meta-atom. i SEM image of fabricated nonlinear metalens. (h) and (i) are reproduced with permission [105] (Copyright 2022, American Association for the Advancement of Science). j Schematic of p2 space group unit. k Experimental intensity distributions (top) on the focal plane and (bottom) along the optical axis. (j) and (k) are reproduced with permission [106] (Copyright 2022, Springer Nature)