Dynamic Evolution of Narrow Spectral Modes in Stochastic Brillouin Random Fiber Lasers

This work reports on the dynamic evolution of narrow linewidth modes in stochastic Brillouin random fiber lasers with ultra-high resolution time-resolved spectroscopy technique. New fundamental aspects are revealed, including strong mode competition in multimode operation. It shows that single-mode operation is only possible near threshold in pulsed regime. Just above threshold, lasing becomes multimode, still in pulsed regime. Well above threshold quasi-CW multimode operation is observed with strong mode competition, exhibiting high-intensity noise, governed by multimode beating, and slow average intensity variations induced by Rayleigh scattering random fluctuations.