Fig. 1. Schematics of phase. (a) Resonance phase is modulated by changing geometric size to achieve 2π phase coverage; (b) geometric size of dielectric rods is altered to change the effective refractive index and achieve 2π phase coverage; (c) artificial atom is rotated to obtain polarization dependent geometric phase; (d) composite phase obtained by combining resonance phase or propagation phase with geometric phase

Fig. 2. Single-function metasurface. (a) SEM images of a resonant phase metasurface consisting of V-shaped antennas and wavefronts for sub-wave sources with different resonance phases^[9]; (b) schematic of an efficient meta-coupler and near-field test results^[17]; (c) far-field experimental test results of an anomalous deflector consisting of gold nanorods of different sizes and its sample images^[18]; (d) SEM photos and schematic diagram of polarization-insensitive meta-lens achieved by modulating propagation phase by varying diameter of TiO₂ dielectric rods^[62]; (e) schematic diagram of a geometric phase metasurface consisting of a single metal layer of rotating metal nanorods to realize photonic spin Hall effect in near infrared band^[67]; (f) photo of highly efficient all-dielectric meta-lens sample operating in visible band and characterization of imaging quality in different wave bands^[23]

Fig. 3. Multifunctional imaging. (a) Experimental results of chiral holography based on an all-dielectric composite phase metasurface and its sample photos^[47]; (b) experimental results of bright- and dark-field imaging based on a composite phase metasurface^[68]; (c) schematic diagram of a chiral holographic imaging device with spin decoupling achieved by designing non-mirror symmetric chiral meta-atoms^[70]; (d) schematic diagram of deep-ultraviolet dual holographic imaging^[48]

Fig. 4. Multifunctional meta-couplers. (a) Schematic diagram of an efficient microwave near- and far-field spin decoupling device and test structure^[58]; (b) schematic diagram of an efficient terahertz near-field bifunctional device and experimental test results of surface wave focusing and deflection in different regions^[56]; (c) near- and far-field bifunctional integration in 850-950 nm band^[72]; (d) efficient coupling between a near-field bifunctional device in optical band and an on-chip optical waveguide^[57]

Fig. 5. Multifunctional wavefront modulation devices. (a) Schematic diagram and test results of a device converting incident light with different chirality into vortex light with different orders^[50]; (b) schematic diagram of transmissive bifocal spin decoupling consisting of V-shaped nanopore arrays^[53]; (c) reflective spin decoupling device based on a two-layer composite phase metasurface realizing different functions at different frequencies^[74]; (d) efficient spin decoupling holography in terahertz band achieved using composite phase based on efficient meta-atoms with a high aspect ratio (20∶1) ^[75]; (e) schematic diagram of a terahertz all-dielectric transmissive spin decoupling vector Bessel beam generator and its test results^[76]; (f) near-infrared reflective vector spin decoupling optical device for different orders and test results for rod and angular polarization vector vortex light^[77]