Fig. 1. Traditional diffractive optical elements used in the generation of vortex beam. (a) Spiraling phase plate; (b) simulated phase pattern; (c) holographic grating

Fig. 2. Real images for two spatial light modulators. (a) Liquid-crystal spatial light modulator; (b) digital micromirror device

Fig. 3. Trait of DMD as an optical switch and its inner structure

Fig. 4. Principle of focusing light through scattering medium. (a) Random speckle formed by the unmodulated beam through scattering medium; (b) focusing light obtained by the modulated beam through scattering medium

Fig. 5. Comparison of focusing effect between slow and high-speed wavefront modulation systems when light travels through a transient medium^[27]. (a) (b) Holograms recording in a low or high-speed wavefront modulation system; (c) (d) intensity profiles after optically reading the corresponding holograms

Fig. 6. DMD-based high-speed wavefront modulation system^[32]. (a) Simplified schematic; (b) optical path schematic of the recording step; (c) optical path schematic of the playback step

Fig. 7. 4f optical system used for preparing the structured beams combined with a filter

Fig. 8. Schematic diagram of error diffusion method^[69]. (a) Gray value normalization of grayscale hologram; (b) specific algorithm execution process

Fig. 9. Simulation of using Lee and optimized Lee method to generate high-order Bessel beam (l=1), respectively^[69]. (a) (b) (c) Theoretical high-order Bessel beams; (d) (e) (f) coding results of Lee algorithm; (g) (h) (i) coding results of optimized Lee algorithm

Fig. 10. Schematic diagrams of the super-pixel method^[71]. (a) In the DMD plane, the light field E(x) corresponds to the off and on states of the micromirrors; (b) schmetic of aperture positioned on the Fourier plane; (c) phase responses of the three pixels indicated by grey squares; (d) response of superpixel in the target plane, in which E_superpixel is the sum of the three pixels' responses

Fig. 11. Electric field distribution of a single super-pixel in the target plane^[71]. (a) n=3; (b) n=4

Fig. 12. Schematic diagram of binary amplitude holography based on the deep learning^[73]