Superluminal Propagation Based On Long-cavity Brillouin Fiber Lasing Oscillation

Slow and fast light,also called temporal light pulse manipulation,has attracted much attention owing to a number of practical applications in alloptical communication,high sensitive interferometer,enhancement of nonlinear effect and microwave photonics,etc.Especially,slow and fast light based on stimulated Brillouin scattering(SBS)in optical fibers has become one of the hot spots of research in recent years,because it has some advantages such as working at room temperature and various wavelength,compatible with modern fibber-based communication system and so on.In this dissertation,the superluminal propagation based on long-cavity Brillouin fiber lasing oscillation have been deeply investigated.We achieve a single-frequency Brillouin fiber laser(BFL)by embedding a saturable absorber with unpumped erbium-doped fiber.The distance of superluminal propagation is well extended to over hundreds of meters in optical fibers via the BFL.Furthermore,we observed the optical bistability and the fast light propagation of the Stokes light.We analyze the effects of the multiple-longitudinal-mode(MLM)operation in long-cavity BFL and the modulation signal for the pump power spectral density and the effective Brillouin gain spectrum in theory.We also point out that the effective Brillouin gain bandwidth play an important role in fast light effect.And the formula for the fractional advancement in the BFL is proposed for the first time.The influential factors for the advancement are thoroughly studied.Firstly,the fractional advancement as a function of the cavity length is simulated.And we prove that the MLM operation limits the long-distance superluminal propagation in our experiments.The fractional advancement is also proved to be not relevant for the cavity length in single-frequency BFL.Then we find that the higher modulation frequency and larger modulation depth will decrease the fractional advancement.Furthermore,we research the fast light effect based on the BFL with different fibers as the Brillouin gain media.The results show that the fractional advancement can be enhanced by using the fibers with larger Brillouin gain coefficient and smaller effective mode field area.All these studies contribute to optimizing the long-distance superluminal propagation and are beneficial for potential applications.