Fig. 1. Amplitude and phase distributions generated by LG vortex beam superpositions with equal absolute value and opposite sign of topological charges

Fig. 2. Amplitude and phase distributions generated by LG vortex beam superpositions with unequal absolute value and opposite sign of topological charges

Fig. 3. Amplitude and phase distributions generated by LG vortex beam superpositions with unequal absolute value of positive topological charges

Fig. 4. Amplitude and phase distributions generated by LG vortex superpositions with unequal absolute value of negative topological charges

Fig. 5. Experimental setups. (a) Structural diagram of RFL; (b) generation of spatial path of multi-singularity vortex beam

Fig. 6. Output characteristics of RFL. (a) Evolution of output power with pump power; (b) output spectra under different pump power, with wavelength range of 1025-1155 nm; (c) evolution of 3 dB bandwidth with pump power; (d) signal spectra under different pump power, with wavelength range of 1079.5-1083 nm

Fig. 7. LG vortex beam superpositions with equal absolute value and opposite sign of topological charges, and corresponding holographic gratings

Fig. 8. LG vortex beam superpositions with unequal absolute value and opposite sign of topological charges,and corresponding holographic gratings

Fig. 9. LG vortex beam superpositions with unequal absolute value of positive topological charges, and corresponding holographic gratings

Fig. 10. LG vortex beam superpositions with unequal absolute value of negative topological charges, and corresponding holographic gratings