Fig. 1. Experiment setup of the laser system.

Fig. 2. (a) Output power of the laser as a function of pump power. (b) Spectra at different output powers.

Fig. 3. (a) Beam quality and the ratio of Raman Stokes light. (b) Ratio of IM-FWM light of the laser at different output powers.

Fig. 4. Temperature of passive fiber of the laser at different output powers.

Fig. 5. Near-field intensity distributions captured from camera at (a) 1560 W (Visualization 1) and (b) 1910 W (Visualization 2).

Fig. 6. Time traces of the laser with (a) 50 s period and (b) 100 μs period at different output powers.

Fig. 7. FS of low-frequency time traces with 50 s period.

Fig. 8. Character factor σ as a function of output laser power.

Fig. 9. (a) Output power versus pump power. (b) Beam quality of the laser with bent passive fiber.

Fig. 10. Near-field intensity distributions at several output powers.

Fig. 11. Phase-matching diagrams of the IM-FWM for the 26/400 fiber.