Fig. 1. Basic physical dimension resources of photons

Fig. 2. Methods for vortex beam generation

Fig. 3. Vortex lasers based on discrete components. (a) Polarization vortex laser assisted by conical Brewster prism inserted in cavity^[77]; (b) vortex laser based on off-axis coupled ring-shaped pumping^[78]; (c) vortex laser based on spin-orbital coupling^[79]; (d) vortex laser based on point-defect lens^[80]; (e) vortex laser array based on Yb∶YAG/YV₄ Raman laser^[81]; (f) vortex laser based on metasurface device^[82]

Fig. 4. Structural diagram of BG laser^[86]

Fig. 5. Output intensity and phase distributions of BG laser based on metasurfaces^[86]

Fig. 6. Reconfigurable and tunable OAM laser^[87]. (a) Concept and principle; (b) experimental setup

Fig. 7. Experimental results of mode reconfigurable vortex laser^[87]. (a) Measured spectra; (b) spectrum of OAM_＋3 laser; (c) spectrum of OAM_－10 laser; (d) intensity profile and interferogram of OAM_＋3 laser; (e) intensity profile and interferogram of OAM_－10 laser

Fig. 8. Experimental results of wavelength tunable vortex laser^[87]. (a) Wavelength tunable spectra; (b) spectrum of OAM_＋1 laser at 1550 nm; (c) spectrum of OAM_＋1 laser at 1565 nm; (d) intensity profile and interferogram of OAM_＋1 laser at 1550 nm; (e) intensity profile and interferogram of OAM_＋1 laser at 1565 nm

Fig. 9. Design of multi-vortex laser^[88]. (a) Experimental setup; (b) threshold pump power versus topological charge number of vortex light; (c) image of concentric-ring pattern etched on output coupler; (d) microscopy image of magnified central area

Fig. 10. Information encoding and data transmission based on multi-vortex laser^[88]. (a) Experimental setup; (b) multi-vortex light spot pattern and corresponding hexadecimal coding information encoded by DMD; (c) image transfer

Fig. 11. Vortex lasers based on fiber. (a) Low threshold single-wavelength polarization vortex laser based on few-mode FBG^[89]; (b) low threshold polarization vortex laser based on long period grating^[90]; (c) polarization vortex laser based on pair of few-mode FBGs to realize selective mode operation^[91]; (d) high order vortex laser based on ring cavity^[92]; (e) vortex femtosecond laser based on mode coupler^[93]; (f) vortex laser based on ring-shaped fiber^[94]

Fig. 12. Experimental setup of tunable OAM laser^[95]

Fig. 13. Transmission spectra^[95]. (a) FBG; (b) FPI

Fig. 14. Experimental results of all-fiber wavelength-switchable vortex laser^[95]. (a) Measured spectra; (b) measured intensity profiles and interferograms

Fig. 15. Vortex lasers based on integrated devices. (a) Vertical-cavity surface-emitting vortex laser (VCSEL)^[96]; (b) vortex laser based on lead bromide perovskite^[97]; (c) vortex micro-laser based on InGaAsP/InP platform^[98]

Fig. 16. Structural diagrams of micro-cavity lasers^[101]. (a) Micro-cavity laser for azimuthally polarized vortex beam; (b) micro-cavity laser for radially polarized vortex beam; (c) cross section of vector laser

Fig. 17. Output light field of vortex laser and light field after transmission through fiber^[102]. (a1) Far-field intensity distribution; (b1)-(e1) polarization distributions; (a2) intensity distribution after 2 km fiber transmission; (b2)-(e2) polarization distributions of fiber output field

Fig. 18. Future development trend and prospect of vortex laser