Fig. 1. Nonlinear enhancement based on plasmonic metasurface. (a) U-ring resonators magnetic resonance enhances the generation of second harmonics; (b) Relationship between signal strength of the second harmonic wave and inter-distance of U-ring resonators on the metasurface; (c) When linear surface lattice resonance exists on the metasurface of L-ring resonator, the sparse metasurface gets a second harmonic signal 5 times stronger than the dense metasurface; (d) Due to the existence of nonlinear surface lattice resonance, a signal 30 times stronger than the normal incidence of the fundamental wave is obtained by the oblique incidence of the fundamental wave on the U-ring metasurface; (e) Influence of the mutual orientation of metasurface of L-ring resonator on the second harmonic generation； (f) Asymmetric structures are arranged near symmetrical structures to enhance the generation of second harmonics

Fig. 2. Nonlinear enhancement of all-dielectric metasurfaces. (a) A metasurface consisting of a disk and a rectangular bar is used to enhance the generation of third harmonics by fano resonance；(b) GaAs based all-dielectric metasurface can simultaneously undergo 11 frequency conversion processes； (c) All-dielectric metasurface uses anapole mode to achieve third harmonic generation enhancement and generates 185 nm vacuum ultraviolet light； (d) metasurface of silicon particles, in which the symmetry of silicon particles in the x direction is broken, and the symmetry in the y direction is maintained. The quasi-BIC model is used to enhance the third harmonic by five orders of magnitude; (e) Two different zones are designed on the metasurface of silicon particles: shrinkage and expansion of the hexamer distribution. The third harmonic nonlinear characterization of bulk and edge states can be realized by changing the fundamental wavelength 基于介质超构表面的非线性增强。（a）由介质圆盘和介质矩形棒组成的超构表面，利用法诺共振增强三次谐波的产生；（b）基于砷化镓的全介质超构表面能够同时发生11种频率转换过程；（c）全介质超构表面利用anapole模式实现三次谐波的增强，产生185 nm的真空紫外光；（d） 硅颗粒超构表面，其中硅颗粒x方向对称性破缺，y方向对称性保持，利用准BIC模式使三次谐波获得五个数量级的增强；（e）硅颗粒超构表面上设计两种不同的区域：收缩和扩张的六聚体分布。改变基波波长，可以实现体态、边界态的三次谐波非线性表征

Fig. 3. Resonance enhancement and control of high harmonics. (a) Generation of high order harmonics is enhanced by the use of local surface plasmon resonance of the Bowtie structure. (b) Generation of high harmonics is enhanced by using surface plasmon resonance of three-dimensional waveguide structures; (c) Use of conical metal waveguides and sapphire in solid systems to enhance the generation of high harmonics; (d) Preparation of gold nanoparticle arrays on monocrystalline silicon films; (e) Etching silicon film on sapphire substrate and introducing fano resonance to enhance high harmonics; (f) Focus of the 3rd and 5th harmonics is achieved through the preparation of Fresnel zone plate by gallium ion implantation into the silicon film

Fig. 4. Relation between the harmonic generation and symmetry. (a) Nonlinear circular dichroism of metasurface of G-type element in particular configuration; (b) Nonlinear circular dichroism of S-type element metasurface; (c) Second harmonic and third harmonic nonlinear circular dichroism of the chiral structure with triple and quadruple symmetries respectively; (d) Introducing extrinsic structure chirality by the oblique incidence of fundamental wave on the bent gold nanowire array; (e) Presence of surface lattice resonance enhances the nonlinear circular dichroism on the metasurface of U-ring

Fig. 5. Nonlinear phase control and application based on metasurface. (a) Direction of nonlinear emission is controlled through nonlinear photonic crystals (NPC)； (b) Nonlinear phase grating was used for experimental verification of nonlinear phase； (c) Spin and wavelength-dependent holography； (d) Nonlinear metamaterial holography

Fig. 6. Quantum effects based on surface plasmon. (a) Experimental apparatus and measurement results to verify the true quantum properties of surface plasmon excited separately by entangled photon pairs; (b) Schematic diagram of the experimental apparatus for verifying the energy-time entanglement of the surface plasmon; (c) Sub-poisson statistics of surface plasmon; (d) Schematic diagram of quantum surface plasmon tunnel junction; (e) Direct observation of quantum tunneling between surface plasmon resonators

Fig. 7. Quantum light source based on metasurface. (a) Schematic diagram of quantum light source based on metasurface; (b) Characterization of three and four-dimensional two-photon quantum states; (c) Four Bell states were successfully prepared by adjusting the phase gradient of the metasurface; (d) Characterization of multi-photon quantum light source based on metasurface

Fig. 8. Quantum state manipulation based on metasurface. (a) By using the geometric phase of a metasurface, photons in different spin-polarized states are given different orbital angular momentum; (b) Four Bell states of entanglement between spin and orbital angular momentum of a single photon; (c) Mutual entanglement of spin angular momentum and orbital angular momentum of two photons; (d) On the left is a schematic diagram of quantum state tomography based on the metasurface, and the inset is an SEM image of the metasurface. On the upper right is the nested structure of three different metasurfaces, in the middle is the diagram of the six different polarization states of the metasurface beam splitter, and on the bottom is the relationship between the minimum number of beam splitter and the number of photons; (e) Density matrix of two different two-dimensional two-photon states based on metasurface reconstruction, the fidelity is 95.24% and 98.54%, respectively

Fig. 8. [in Chinese]

Fig. 9. Quantum optical applications based on metasurface. (a) Full absorption of a single photon based on a metal metasurface. The two input channels of the photon α,β, the two output channels of the photon , , and the input and output channels of the surface plasmon , are shown. In the figure below, the normalized count of the photon output channel , changes with the position movement of the metasurface, where the photon output channels are normalized relative to the photon input channels , respectively. The filled circle represents the presence of the two photon input channels and the unfilled circle represents the block of the photon input channel ; (b) Entanglement and disentanglement of NOON state path using metasurface. (c) Signal photon imaging using entangled photon pairs in the above two figures, and different polarization measurements of idle photon can clearly distinguish the triangular and star patterns; the two images below are imaged using mixed photon pairs and cannot clearly distinguish between the two patterns; (d) Experimental setup for quantum weak measurement using a metasurface 基于超构表面的量子光学应用。（a）基于金属超构表面的单光子全吸收。图中α、β表示光子的两个输入通道， 、 表示光子的两个输出通道， 、 表示等离激元的输入、输出通道。图中下方表示 、 光子输出通道的归一化计数随着超构表面位置移动的变化，其中 、 光子输出通道分别相对于 、 光子输入通道归一化。填充的圆形符号代表 、 光子输入通道存在的情况，没有填充的圆形符号代表 光子输入通道被遮挡的情况；（b）使用超构表面实现NOON态路径的纠缠与解纠缠；（c）上方两图中使用纠缠光子对的信号光子成像，对闲置光子进行的不同的偏振态测量，可以清晰地区分开三角形和五角星图案；下方两图中使用混态光子对进行成像，不能将两种图案清晰地区分开；（d）使用超构表面进行量子弱测量的实验装置图

Fig. 10. Quantum vacuum engineering based on metasurface. (a) Based on the metasurface, the quantum vacuum symmetry of the quantum emitter is broken, so that quantum interference between different energy levels of the multi-level quantum emitter occurs. (b) Electromagnetic field radiated by an electric dipole in the x direction above the metasurface can return to focus to the source point along the original path, with the maximum efficiency being 81%, and the electromagnetic field radiated by an electric dipole in the y direction has no such effect; (c) When there is no metasurface, the energy level decayed exponentially and the energy level occupied 0; when the metasurface exists, the decay rate of the energy level decreases, and the energy level population first increases and then decreases; (d) Schematic diagram of quantum entanglement of two quantum emitters based on metasurface; (e) Metasurface enables the electromagnetic field radiated by the source point electric dipole to be oriented to the position of the target electric dipole with the highest efficiency 82%; (f) Concurrence of two quantum emitters varies with the distance between them. The red solid line corresponds to the vacuum condition, and the blue solid line corresponds to the metasurface condition 基于超构表面的量子真空调控。（a）基于超构表面打破量子发光体的量子真空对称性，使得多能级量子发光体的不同能级之间发生量子干涉；（b）超构表面上方沿着x方向的电偶极子辐射的电磁场能够沿原路返回聚焦到源点处，最大效率为81%，沿着y方向的电偶极子辐射的电磁场没有这种效应。（c）当没有超构表面时， 能级单指数衰减， 能级占据数为0；当超构表面存在时， 能级衰减速率变慢， 能级占据数先增大后减小；（d）基于超构表面实现两个量子发光体量子纠缠的示意图；（e）超构表面能够使得源点电偶极子辐射的电磁场能够定向地聚焦于目标电偶极子的位置，效率最高为82%；（f）两个量子发光体的并发性随着两者之间距离的变化，红色实线对应于真空条件，蓝色实线对应于超构表面条件下