Research On Slow-Light Propagation Based On Stimulated Brillouin Scattering In Optics Fibers

SBS slow light has been at the research focus in slow light optics community since the fast and slow light based on Stimulated Brillouin scattering (SBS) was proposed by D. J. Gauthier in 2004. Due to the inherent characteristics of SBS, there are still two problems in SBS slow light: the limited slow light delay time and the narrow Brillouin gain linewidth. To address the two problems, this dissertation proposes some innovative solutions, and performs theoretical and experimental studies.First, we theoretically study the SBS fast and slow light in an optical fiber based on the SBS coupled wave equations. We study the analytic solutions in stable state with small-signal and the numerical solutions in stable state and transient state, respectively. In the case of stable state with small-signal, SBS slow light delay time can be expressed by an analytic expression, which is proportional to the Brillouin gain parameter and inversely proportional to the Brillouin gain linewidth; while in region of gain saturation, due to the effect of pump depletion, the delay time becomes decreasing and even negative. In the case of transient state when probe pulse duration is smaller than phonon lifetime, a new pulsle induced by the delayed acoustic wave adds an additional delay time and induces large pulse distortion and broadening.Second, to extend the controllable delay time, we propose a method based on a Brillouin optical fiber ring amplifier where the probe pulse can be amplified with multiple times in it. In experiment, a maximum time delay of 215 ns, larger than five times of the input probe pulse duration of 40 ns, has been obtained after experiencing eight loops of Brillouin amplification.Finally, to broaden SBS linewidth, we propose a method to obtain broadband Brillouin gain linewidth by overlapping multiple gain spectrums, and a method to obtain multiple equal-amplitude spectral lines using the technique of multi-frequency phase modulation. First, we have theoretically and experimentally obtained three, five, seven, nine and eleven equal-amplitude spectral lines, respectively; then we have performed the broadband SBS slow light experiment using pump with multiple equal-amplitude spectral lines, obtaining a maximum Brillouin linewidth of 900 MHz using eleven equal-amplitude spectral lines with the fundamental frequency of 30 MHz. The experimental results also indicate that broader flattened Brillouin gain spectrum can produce larger fractional delay at a fixed broadening factor.