Fig. 1. Random fiber laser with full-open and half-open cavity structures. (a) Full-open cavity; (b) half-open cavity

Fig. 2. High-power random fiber laser oscillators. (a) 100.7 W polarized random fiber laser in 2017^[26]; (b) 418 W random fiber laser in 2017^[27]; (c) 919 W random fiber laser in 2019^[28]; (d) 1570 W random fiber laser in 2021^[29]; (e) 1277 W full-open cavity random fiber laser in 2022^[30]; (f) 1972 W full-open cavity random fiber laser in 2023^[31]

Fig. 3. Schematic diagram of random fiber laser amplifier system

Fig. 4. 10.14 kW cascaded pumped random fiber laser amplifier in 2022^[41]. (a) System structure; (b) output spectra

Fig. 5. Power and linewidth of representative high-power random fiber laser amplifiers in recent years

Fig. 6. Schematic diagram of wavelength-tunable point feedback component

Fig. 7. Wavelength-tunable ytterbium-doped gain random fiber laser^[43]

Fig. 8. Wavelength-tunable erbium-doped gain random fiber laser^[44]

Fig. 9. Wide spectral range operating Raman scattering gain random fiber lasers. (a) Raman random fiber laser with operating wavelength covering from 1.0 μm to 1.9 μm^[49]; (b) high spectral purity Raman random fiber laser pumped by amplified spontaneous emission source^[50]

Fig. 10. Random fiber lasers with Raman gain for hybrid gain 10 kW-level power amplification. (a) High spectral purity random Raman fiber laser^[59]; (b) 10 kW-level hybrid gain power amplification structure^[60]; (c) evolution of output power, 3dB bandwidth, and output spectrum at maximum power^[60]

Fig. 11. Two schemes for generating supercontinuum output. (a) Supercontinuum output generated by fiber mirror feedback semi-open cavity random fiber laser^[66]; (b) supercontinuum output generated by fiber loop feedback semi-open cavity random fiber laser^[69]

Fig. 12. Experiment of supercontinuum output generated by full-open cavity structure random fiber lasers^[73]

Fig. 13. Power-amplified random fiber laser near threshold generating 2.4 kW supercontinuum output^[77]

Fig. 14. Two schemes for generating supercontinuum output. (a) Semi-open cavity random fiber laser generating 1.3 kW supercontinuum output^[79]; (b) full-open cavity random fiber laser generating 3.18 kW supercontinuum output^[80]

Fig. 15. Research on speckle-free imaging based on random fiber lasers. (a) Structure, imaging system, and speckle-free imaging effect of multimode coherent polymer random fiber laser^[88]; (b) semi-open cavity random fiber laser used for comparative speckle-free imaging effects of single-mode and multimode fibers^[89]; (c) output field after transmission through single-mode and multimode fibers for random fiber laser, amplified spontaneous emission source, and narrow linewidth laser^[89]; (d) speckle-free imaging after passing through liquid milk for random fiber laser and amplified spontaneous emission source^[89]

Fig. 16. Research on single-core multimode fiber imaging using random fiber laser as the illumination source^[94]. (a) Optical path structure of single-arm multimode fiber imaging system; (b) structure of semi-open cavity random fiber laser utilizing 30 km passive fiber Rayleigh scattering for feedback; (c) comparison of multimode fiber image reconstruction results using five different fiber lasers (RFL: random fiber laser; NLL: narrow linewidth fiber laser; CFL: conventional fixed-cavity fiber laser; NASE: narrow-band ASE source; BASE: broad-spectrum ASE source); (d) resolution test results of five different fiber lasers in the same multimode fiber imaging system