The nonlinear dynamics of cw-pumped Brillouin long-fiber ring lasers that contain a large number of longitudinal modes N beneath the Brillouin gain curve is controlled by a single parameter, namely, the Stokes feedback R. Below Rcrit, a stable train of dissipative solitonic pulses is spontaneously structured at the round-trip frequency fr without any additional intracavity mode locking. Experimental observations in cw-pumped fiber ring cavities, supported by numerical simulation in a coherent space–time three-wave model that includes the optical Kerr effect, prove the universality of the self-pulsing mechanism. Stability analysis shows that below Rcrit the steady Brillouin mirror regime is destabilized through a Hopf bifurcation. For R<Rcrit<R0 the bifurcation is supercritical and exhibits an asymptotically monostable oscillatory regime at twice fr for high enough N or at fr for lower N, in a finite transition region. For R0<R<Rcrit, the bifurcation is subcritical and exhibits dynamic bistability between the steady and the pulsed regimes in a finite hysteresis region whose width is proportional to the Kerr parameter. For R small enough, the cavity longitudinal modes merge into a dissipative solitonic Brillouin pulse: the dynamic three-wave model yields self-structured asymptotically stable trains of pulses for any initial conditions, in fair quantitative agreement (for pulse width, intensity, shape, and period) with the experiments in the entire self-pulsing domain. Amplification of spontaneous emission breaks down the stable-pulse regime in long devices (i.e., high N), so the fiber noise amplitude is higher than the coherent amplitude that separates two consecutive pulses.
© 1999 Optical Society of America
(060.5530) Fiber optics and optical communications : Pulse propagation and temporal solitons
(140.3560) Lasers and laser optics : Lasers, ring
(190.1450) Nonlinear optics : Bistability
(290.5900) Scattering : Scattering, stimulated Brillouin
Carlos Montes, Derradji Bahloul, Isabelle Bongrand, Jean Botineau, Gérard Cheval, Abdellatif Mamhoud, Eric Picholle, and Antonio Picozzi, "Self-pulsing and dynamic bistability in cw-pumped Brillouin fiber ring lasers," J. Opt. Soc. Am. B 16, 932-951 (1999)