Fig. 1. Experimental setup of the vortex RFL system. (a) Generation setup of the vortex RFL. (b) Interference setup of the vortex RFL. WDM, wavelength division multiplexer; FBG, fiber Bragg grating with central wavelength at 1092.1 nm; PBS, polarization beam splitter; BS, beam splitter; SLM, spatial light modulator; CCD, charge-coupled device.

Fig. 2. (a) Normalized amplitude spectra of a 1092.1 nm random laser at different pump powers. (b) Output power evolution of RFL at different pump powers.

Fig. 3. (a) Holograms loaded onto the SLM. (b) Intensity distribution. (c) Interference fringes of the vortex RFL acquired by a CCD. The topological charge l is 1 to 5 from left to right.

Fig. 4. (a) Holograms loaded onto the SLM. (b) Intensity distribution. (c) Interference fringes of the vortex RFL acquired by a CCD. The topological charge l is −5 to −1 from left to right.

Fig. 5. (a) Holograms loaded onto the SLM. (b) Intensity distribution. (c) Interference fringes of the vortex RFL acquired by a CCD. The topological charge l is 10, 20, and 50 from left to right.

Fig. 6. (a) Holograms loaded onto the SLM. (b) Intensity distribution. (c) Interference fringes of vortex RFL acquired by a CCD. The topological charge l is 1.5 and 2.5 from left to right.