Fig. 1. Detecting structure and results of transmission spectra of acoustic-induced fiber grating (AIFG). (a) Schematic diagram of detecting; (b) transmission spectra of LP₀₁ mode at loaded electrical signals of different frequencies

Fig. 2. Structure diagram of cascaded random Raman fiber laser based on AIFG

Fig. 3. Experimental results of output characteristics of cascade Raman fiber laser. (a) Total output power and inband power of each Raman Stokes as a function of pump power; (b) normalized linear spectrum at peak power of each Raman Stokes; (c) spectral purity of each Raman Stokes; (d) efficiency of each Raman Stokes

Fig. 4. Results of laser stability test. (a) Power fluctuation of each Raman Stokes; (b) normalized spectrum stability of the 6^th Raman Stokes

Fig. 5. Self-interference setup of vortex random Raman fiber laser

Fig. 6. Spectrum, original beam profile, LP₁₁ mode beam profile, and self-interference pattern of each vortex random Raman Stokes