Fig. 1. Planar functional liquid crystal devices. (a) Fresnel liquid crystal lens^[3]; (b) liquid crystal spiral phase plate^[4]; (c) tunable liquid crystal grating^[5]; (d) liquid crystal beam steering device^[6]

Fig. 2. Schematics of liquid crystal molecule arrangement. (a) Smectic liquid crystal^[26]; (b) nematic liquid crystals^[26]; (c) cholesteric liquid crystal^[26]; (d) blue phase liquid crystal^[24]

Fig. 3. Molecular modulation mechanism of liquid crystal. (a) Structural diagram of liquid crystal molecular; (b) amplitude modulation properties of liquid crystals; (c) geometric phase modulation properties of liquid crystals

Fig. 4. Various optical orientation technology systems. (a) Mask exposure system^[40]; (b) interference exposure system^[39]; (c) direct write exposure system^[37]; (d) DMD dynamic mask exposure system^[38]; (e) plasmon mask exposure system^[41]; (f) SLM dynamic mask exposure system^[36]

Fig. 5. Principle and applications of liquid crystal display. (a) Structural diagram of liquid crystal display; (b) applications of liquid crystal display

Fig. 6. Principle and applications of amplitude type spatial light modulator. (a) Holoeye LC2012 amplitude type spatial light modulator and its principle^[48]; (b) laser beam shaping realized by using space light modulator^[49]; (c) schematic of adjustable refraction instrument for measuring refractive index based on spatial light modulator^[50]

Fig. 7. Smart windows based on liquid crystal. (a) Schematic of smart window based on liquid crystal/graphene composites^[60]; (b) schematic of stable and expandable smart window based on polymer material liquid crystal^[61]

Fig. 8. Principle and applications of phase type spatial light modulator. (a) Holoeye PLUTO-2 phase type spatial light modulator and its principle; (b) scalable all-optical neural network based on spatial optical modulator^[64]; (c) encryption system based on phase type spatial light modulator^[65]

Fig. 9. Dynamic encryption systems based on spatial light modulator. (a) Holographic encryption of orbital angular momentum based on space light modulator^[66]; (b) spatial nonlinear optical image encryption based on spatial light modulator^[67]

Fig. 10. Geometric phase liquid crystal devices. (a) Dual-frequency liquid crystal polarization grating based on geometric phase^[68]; (b) polarization switching liquid crystal lens based on geometric phase^[69]; (c) liquid crystal bifocal lens based on geometric phase^[70]; (d) cholesteric liquid crystals under different phase distributions^[71]; (e) self-assembling spiral superstructure with optically controlled chiral inversion^[72]

Fig. 11. Dynamic encryption systems based on liquid crystal. (a) Schematic of encryption system for transmission of tunable circularly polarized luminescent signals based on dye-doped chiral liquid crystals^[73]; (b) schematic of high security liquid crystal holographic encryption system inspired by Tiger Amulet^[74]

Fig. 12. Multifunctional liquid crystal devices based on geometric phase. (a) Multifunctional liquid crystal device for simultaneous display of near-field and far-field images^[75]; (b) liquid crystal device with polarization, wavelength, and position multiplexing^[76]

Fig. 13. Multifunctional liquid crystal device with surface display and far-field holographic display^[79]. (a) Complex amplitude modulation of liquid crystal molecules in orthogonal polarized light paths; (b) schematic of device design principle; (c) experimental test results

Fig. 14. Multifunctional liquid crystal device with multi-channel surface image display and far-field holographic display^[80]. (a) Relationship between normalized strength of liquid crystal molecules and orientation angle θ before and after rotation; (b) four orientation angles of liquid crystal molecules and their corresponding binary intensity codes; (c) experimental test result

Fig. 15. Modulator components with integrated liquid crystal and metasurface. (a) Schematic of optical encryption system with integrated polymer dispersed liquid crystal and metasurface^[90]; (b) schematic of device with integrated nematic liquid crystal and metasurface^[91]

Fig. 16. Liquid crystal-metasurface dynamic control devices. (a) Schematic of electrically tunable multifunctional polarimetric dependent metasurface with integrated liquid crystal^[92]; (b) schematic of electrically tunable liquid crystal loaded metasurface^[93]

Fig. 17. Tunable liquid crystal micro laser devices. (a) Wide-band and dual outgoing liquid crystal laser^[97]; (b) blue phase liquid crystal laser with wide temperature domain^[98]

Fig. 18. Nonlinear light field control based on liquid crystal. (a) Study on nonlinear properties of ferroelectric nematic liquid crystals^[112]; (b) nonlinear property system based on spiral ferroelectric nematic liquid crystals^[113]

Fig. 19. Control of angular momentum of light field based on liquid crystal devices. (a) Three-dimensional array of orbital angular momentum beams based on geometric phase of liquid crystal^[114]; (b) four-dimensional optical tunable liquid crystal device^[115]