Fig. 1. Subwavelength grating^[4-5]

Fig. 2. Photonic crystals. (a) One-dimensional photonic crystal^[9]; (b) (c) two-dimensional photonic crystals^[10-11]; (d) three-dimensional photonic crystal^[12]

Fig. 3. Metasurfaces. (a) Metal antenna metasurface^[19]; (b) propagation phase metasurface^[20]; (c) geometric phase metasurface^[21]

Fig. 4. Schematic of grating waveguide coupler. (a) Surface relief grating; (b) volume holographic grating; (c) liquid crystal polarization volume grating

Fig. 5. Surface relief gratings applied to AR displays. (a) Two-photon interference processing^[40]; (b) U-shaped grating^[41]; (c) deep-slot grating^[42]

Fig. 6. Volume holographic gratings applied to AR displays. (a) Full color AR display^[6]; (b) photopolymer volume holographic grating^[43]; (c) high efficiency achromatic display^[44]; (d) large field of view^[45]

Fig. 7. Liquid crystal polarization volume gratings applied to AR displays. (a) Color waveguide display^[47]; (b) flexible PVG^[48]; (c) large field of view^[49]

Fig. 8. Near eye display based on metasurface. (a) Expanded field of view scheme^[50]; (b) reduced chromatic aberration scheme^[51]; (c) contact lens integrated AR display^[52]; (d) large achromatic metalens^[53]

Fig. 9. Metasurface holography. (a) 3D holographic display^[55]; (b) dual-wavelength holography^[56]; (c) on-chip holographic multiplexing^[57]; (d) polarization multiplexing holography^[58]; (e) polarization dynamic modulation^[59]; (f) liquid crystal dynamic modulation^[60]