Fig. 1. Light-emitting metasurfaces for manipulating and controlling light directional emission^[18]

Fig. 2. Application of light-emitting metasurfaces in the field of lighting. (a) Schematic diagram of phosphor conversion LED emission^[24]; (b) left panel displays a scanning electron microscope (SEM) photograph of Al nanoparticle arrays (inset: a schematic diagram of the metasurface integrating a phosphor conversion layer), right panel displays a comparison of structured emission brightness without/with integrated antenna arrays^[25]; (c) schematic diagram and SEM image of InGaN/GaN quantum well metasurface, as well as the phase and amplitude of light from the luminescent metasurface into the substrate as a function of the width of the nanopillar^[27]; (d) schematic illustration of commercial GaN-based LEDs with disordered Ag nanoparticle arrays deposited on the top^[29]

Fig. 3. Metasurfaces for high-definition display^[35]. (a) Schematic diagram of the OLED with integrated metasurface reflector (meta-OLED); (b) left panel shows the electroluminescence image of meta-OLED with high-density RGB pixels under an optical microscope, right panel shows optical microscopic imaging of meta-OLED with variable periodicity control for tuning emission colors. The two horizontal sections correspond to nanocylinder diameters of 100 nm and 120 nm, while the vertical section corresponds to thicknesses of 135 nm and 165 nm for blue and green OLED panel backgrounds, respectively; (c) comparison of electroluminescence spectra between meta-OLED (solid line) and bare OLED (dashed line); (d) variation of luminance for RGB emissions with current density, where the slope represents the luminous efficiency

Fig. 4. Metasurfaces for communication front-end. (a) Schematic diagram of planar and spherical fluorescent detectors^[36]; (b) compound parabolic concentrator with integrated blazed grating (top to bottom: structural schematic, actual photograph, and field-of-view angle distribution in the xz plane)^[37]; (c) schematic diagram of a broad-angle detection and collimated emission metasurface (inset: radiation distribution in momentum space)^[38]; (d) top to bottom: schematic diagram of a plasmonic nanocavity structure, simulated (solid line) and measured (symbols) angular distribution of radiation direction (blue) and excitation rate (red), and normalized time-resolved fluorescence spectra from dye on a glass substrate (blue) and dye coupled to the plasmonic nanocavity (red), with the black dashed line representing the instrument response function (IRF) ^[12]

Fig. 5. Metasurface for X-ray detection coupler. (a) Top is the tunable luminescence spectra of perovskite quantum dots under X-ray irradiation, bottom is the bright-field imaging (left) and X-ray imaging (right) of perovskite nanocrystal scintillators^[43]; (b) radiation diagrams and corresponding intensity ratios of YAG∶Ce plates with integrated nano antennas in forward of P_for, lateral P_side, and backward P_back, and bottom right is the comparison of luminescence intensities of YAG∶Ce plate between uncoupled and coupled nanoantenna^[44]; (c) schematic diagram of the light extraction mechanism of BGO scintillator enhanced by multi-scale nanosphere structure (MSSN), as well as the normal emission enhancement spectrum of BGO scintillator integrated with MSSN and photonic crystal (PhC) under X-ray excitation^[45]

Fig. 6. Metasurface for chiral light emission. (a) Chiral coupling of valley excitons in a transition metal dichalcogenide monolayer with spin-momentum locked surface plasmons at room temperature (upper layer represents the bright-field microscopy images, SEM images, and fluorescence microscopy images of homogeneous gold nanohole arrays integrated with monolayer WS₂ ^[46], lower layer represents the SEM images of gold nanohole arrays with Pancharatnam-Berry phase and the differential fluorescence dispersion spectra for left and right circularly polarized excitations)^[47]; (b) schematic diagram of a dual-layer chiral emitter device composed of perovskite nanoparticles embedded in polyacrylonitrile^[52]; (c) left is schematic diagram of superstructure surface units with broken in-plane and out-of-plane symmetries, and the role of chiral polarization emission in angle-dependent emission spectra, right is circularly polarized emission spectra on the upper and lower thresholds in the normal direction^[53]; (d) schematic diagram of spin-locked valley-directed emission achieved using nanopillar with a gap perovskite metasurface^[54]

Fig. 7. Fabrication and optical properties of c-Si metasurfaces^[15]. (a) Schematic diagram of the fabrication process of c-Si metasurfaces on a quartz substrate, real image of the particle array retrieved by the “float off”, and bright-field microscope images; (b) refractive index and extinction coefficient of commonly used dielectric and semiconductor materials at a wavelength of 600 nm; (c) (d) simulated dispersion spectra of extinction and photoluminescence enhancement in c-Si metasurfaces, where white dashed lines correspond to in-plane diffraction orders (-1,0) and (1,0)

Fig. 8. c-Si Metasurfaces for manipulating photon radiation. (a) Schematic diagram of c-Si metasurface for enhancing directional emission from monolayer WS₂^[17]; (b) spatial distribution of radiative intensity in momentum space for the light-emitting metasurface^[17]; (c) left is schematic diagram of c-Si metasurface integrated with dye film, along with corresponding bright-field and fluorescence microscopy images, right is schematic diagram depicting symmetry-protected BIC near-field enhanced molecular dipole emission^[16]; (d) left is near-field radiation distribution of electric quadrupole when the lattice approaches in-plane diffraction limit, right is emission spectra of light-emitting metasurface and bare dye film, with the insert displaying the far-field radiation pattern of quasi-BIC, where the black double arrows indicate the direction of polarization rotation^[16]

Fig. 9. Metasurface for manipulating weakly coupled lasing. (a) Schematic diagram of a plasmon lasers^[84]; (b) plasmonic nanolasers based on CdS nanowire-MgF₂ layer-Ag film hybrid structure (inset: scanning electron microscope image)^[85]; (c) plasmonic array lasers based on gold nanoparticle arrays^[87]; (d) InGaAsP multiple quantum wells cylindrical nanoresonator arrays suspended in air^[88]; (e) GaAs nanoresonator array exhibiting quasi-BIC leaky resonant mode^[90]; (f) TiO₂ metasurface integrated with CdSe/CdZnS colloidal film generating laser emission (red beam) under excitation by pump light (green cone) ^[93]; (g) lasing from Si₃N₄ hybrid lattice metasurface^[97]

Fig. 10. Exciton-polaritons condensation and lasing. (a) Energy-momentum dispersion relations between exciton-polaritons, photons, and excitons^[101]; (b) observation of polaritons BEC in the emission spectrum of CdTe microcavity at 5 K temperature^[105]; (c)condensation of exciton-polaritons in integrated monolayer WS₂ microcavities at room temperature, with verification of their temporal and spatial coherence^[112]; (d) plasmon-exciton-polaritons condensation achieved through strong coupling between SLR on metasurface and organic dye molecules^[110]; (e) low-threshold exciton-polaritons condensation and lasing realized by strong coupling between one-dimensional GaAs grating-supported BIC and quantum wells at 4 K low temperature^[113]; (f) exciton-polaritons lasing achieved through strong coupling between SLR on silicon metasurface and organic dye molecules^[114]; (g) exciton-polaritons lasing with vortex polarization enabled by strong coupling between the BIC mode supported by silicon metasurface and organic dye molecules^[115]