Fig. 1. Experimental setup of the 1.7 μm high-power vortex RFL

Fig. 2. Experimental results of output characteristics of the 1.7 μm band fiber random laser. (a) Relationship between output power and residual pump power and the pump power; (b) relationship between power ratio and optical to optical conversion efficiency and the pump power; (c) evolution of output spectrum with different output powers

Fig. 3. Experimental results of output characteristics of the 1.7 μm band vortex RFL. (a) Transmission spectrum of the spiral LPFG; (b) relationship between output power and slope efficiency and incident power; (c) evolution of the output spectrum with different output powers

Fig. 4. Theoretical simulation results and experimental measurement results of the intensity profiles of reference Gaussian beam, first order vortex beam, interference pattern between first order vortex beam, and reference Gaussian spherical wave. (a)-(c) Theoretical simulation results; (d)-(f) experimental measurement results

Fig. 5. Vortex RFL. (a) Short time temporal trace; (b) radio frequency spectrum