Fig. 1. Schematic diagrams of phase gradient control and phase matching. (a) Direction of light propagation is opposite to that of phase gradient^[36]; (b) direction of light propagation is the same as that of phase gradient^[36]; (c) coupling free light field into waveguide propagation mode by phase matching^[40]

Fig. 2. Schematic diagrams of devices using surface plasmon and mode converter. (a)(b) Structure diagrams of metal antenna array on one dimensional dielectric silicon nitride waveguide^[47]; (c) schematic diagram of waveguide mode converter^[52]

Fig. 3. Design of on-chip super surface lens using effective refractive index^[46]. (a) Effective refractive indexes of gold blocks with different lengths varying with wavelength; (b) change of effective refractive index with the length of gold block at selected wavelength; (c) curve of effective refractive index at each point

Fig. 4. Structure schematic of metasurface design using transfer matrix. (a)(b) Schematic diagram of waveguide mode converter^[52]; (c)(d) schematic diagram of antenna coupler for arbitrary polarization^[39]

Fig. 5. Structural diagram of metasurface dispersionless lens^[56]

Fig. 6. Schematic diagrams of metasurface beam splitter. (a) Schematic diagram of metasurface mode beam splitter^[48] ; (b) for TE and TM modes, schematic diagrams of the effective refractive index of the metasurface^[48] ; (c) electron micrograph of metasurface wavelength beam splitter^[57] ; (d) transmission change of different channels with different wavelengths^[57]

Fig. 7. Structure diagrams of metasurface on-chip coupler. (a) Structure diagram and electron microscope photo of photonic crystal structure coupler^[41]; (b) schematic diagram of antenna structure coupler^[39]

Fig. 8. Metasurface mode converter. (a) Schematic diagram of metasurface mode converter^[55]; (b) transmission curves of various waveguide modes^[55]; (c) electron micrograph of metasurface mode converter^[52]; (d) mode conversion efficiency curves of various waveguide modes^[52]

Fig. 9. Metasurface dispersionless lens and convolver^[56]. (a) Electron micrograph of metasurface dispersionless lens; (b)(c) intensity distribution at focal plane of metasurface lens for 1000 nm and 1550 nm; (d)(e) theoretical calculation, numerical simulation and experimental results of metasurface convolver for 1000 nm and 1550 nm

Fig. 10. Asymmetric propagation waveguide^[36]. (a) Structure diagram of asymmetric propagation waveguide; (b) transmission distribution of incident TE fundamental mode from the left; (c) transmission distribution of incident TE fundamental mode from the right