Fig. 1. Natural materials are made of “real atoms” (left) and metamaterials are made of “artificial meta-atoms” (right)

Fig. 2. Electromagnetic wave manipulations. (a)Electromagnetic wave manipulations with bulky device relying on the propagation phase; (b) electromagnetic wave manipulations with metasurface relying on the abruptly changed phase

Fig. 3. Development from homogeneous metamaterials (MMs), inhomogeneous MMs to gradient metasurfaces (MSs)

Fig. 4. Representative research works of Prof. Lei Zhou’s group from Fudan University in the field of metasurfaces

Fig. 5. Principle of electromagnetic polarization manipulation with metasurfaces

Fig. 6. Electromagnetic polarization manipulations with metasurfaces. (a) Reflective metasurface for high-efficiency polarization manipulations^[13]; (b) reflection phase spectra of reflective metasurface for different polarization cases^[13]; (c) ABA-multilayer transmission-type metasurface^[19]; (d) three typical polarization manipulation effects^[19]

Fig. 7. Arbitrary electromagnetic wavefront manipulations via freely controlling the spatial reflection (or transmission) phase distributions on the metasurface

Fig. 8. Schematic pictures and experimental demonstrations to respectively achieve anomalous reflection and surface wave excitation with reflective metasurfaces of different gradient phases. (a)--(c) Anomalous reflection; (d)--(f) surface wave excitation

Fig. 9. Comparison of traditional surface plasmon coupler and new metasurface coupler. (a) Two key issues degrading the performance of traditional surface plasmon coupler, i.e., reflection loss and decoupling loss; (b)(c) new metasurface coupler suppresses two losses and realizes high-efficiency surface plasmon excitation

Fig. 10. Photonic spin Hall effect realized by Pancharatnam-Berry metasurface. (a) Jones matrix analysis of the meta-atom array; (b) principle of the Pancharatnam-Berry phase based on Poincaré sphere; (c)(d) photonic spin Hall effect achieved in the Pancharatnam-Berry metasurface

Fig. 11. Switchable functionalities achieved by tunable metasurface via changing electromagnetic phase dynamically

Fig. 12. Different electromagnetic functionalities achieved by reflective metasurfaces. (a)(b) Schematics of reflective metasurface and single-port resonator model based on coupled-mode theory; (c)(d) diagrams of the absorption and the span of reflection phase inside the metasurface as a function of Q_r and Q_a

Fig. 13. Widely tunable phase manipulation with graphene based metasurfaces. (a) Schematic of the graphene based tunable metasruface; (b) Smith curves of the reflection coefficient for the metasurface at different phase regions, i.e., underdamping, critical damping and overdamping; (c)(d) the dynamical reflection phase manipulations of the metasurface with different gate voltages