掺铒光纤中浓度效应对光脉冲群速的影响

Effect of Ion Density on Slow Light Propagation in Erbium-Doped Optical Fiber

利用相干布居振荡技术在介质吸收光谱上产生烧孔,孔宽大约为基态粒子数恢复时间的倒数.由增益理论分析得出不同抽运光强度对介质吸收状态的影响.在介质的吸收区域,振荡导致光脉冲经历饱和吸收,脉冲传输延迟;在介质的增益区域,振荡又导致光脉冲经历增益饱和、脉冲传输超前.将此技术应用在掺铒光纤(EDOF)中实现了光速人为可控.根据布居振荡效应及增益理论,由速率方程出发,得到了探测光的群折射率的理论解析表达式.考虑掺铒浓度对光脉冲群速度的影响,分别对四种浓度的光纤进行实验研究,观测到的最慢群速分别为3.45×102m/s,相应感生群折射率8.7×105.

In the absorption spectrum of the medium, a burned hole is appeared by coherent population oscillation, and the linewidth of this feature is approximately the inverse of the ground state population recovery time. Based on the theoretical analysis of gain, the effect of absorption on the different pump powers is obtained. In the medium absorption range, the oscillation leads the pulse to experience absorption saturation and propagation delay; in the medium gain range, this effect induces the pulse to experience gain saturation and propagation advance. Making use of coherent population oscillation we can control the group velocity of light propagation in erbium-doped optical fiber. According to coherent population oscillation and gain theory, the analytic expression of the group index from rate equation is obtained. In the experiment the slowest group velocity was 3.45×10^2 m/s, and the corresponding group index was 8.7×10^5. The simulation results are quantitatively coincident with the experimental data.