Raman-driven destabilization of mode-locked long cavity fiber lasers: fundamental limitations to energy scalability

We report on the destabilization of the mode-locking operation of a long cavity fiber laser. We show that the destabilization is accompanied by the abrupt emergence of a strong frequency-downshifted Stokes signal, and simultaneously, we find that the laser output displays characteristics typical of noise-like pulses. We use numerical simulations to illustrate how the Stokes signal grows from stimulated Raman scattering and plays a key role in the destabilization of the laser output. Our results indicate that stimulated Raman scattering may impose an ultimate limit on the energy scalability via cavity lengthening. (C) 2013 Optical Society of America