Optical turbulence and spectral condensate in long-fiber lasers

We study optical wave turbulence using as a particular example recently created ultralong-fiber laser. We show that the sign of the cavity dispersion has a critical impact on the spectral and temporal properties of generated radiation that are directly relevant to the fiber laser performance. For a normal dispersion, we observe an intermediate state with an extremely narrow spectrum (condensate), which experiences an instability and a sharp transition to a strongly fluctuating regime with a wide spectrum and increased probability of spontaneous generation of large-amplitude pulses.

Figure 1

(Color online) Generated power vs time for different values of dispersion and pump powers. Inset: power variance vs the mean for ${\beta }_{2}L=150{\text{ps}}^2$.

Figure 2

(Color online) Time dependence of the modes with $n=0$ (blue), $n=5$ (green), and $n=10$ (red). Inset: spectra before and after condensate destruction, averaged between 550 and 650 round trips (blue) and between 850 and 950 round trips (green).

Figure 3

(Color online) Spectra of generated radiation for different ${\beta }_{2}L$.

Figure 4

(Color online) Spectral bandwidth (diamonds) and generated power (stars) vs ${\beta }_{2}L$.

Figure 5

(Color online) Amplitude correlation functions for the central mode.

Figure 6

(Color online) Histograms of total generated power for normal and anomalous dispersions.