Nonlinear propagation of pulses in multimode fiber with strong linear coupling

Multimode fiber has a richer spatial dimension than single-mode fiber, and is an ideal platform for studying many novel nonlinear effects. We established a strong linear coupling and short-range fiber model to understand the interactive effects of linear coupling and nonlinear effects. We find that strong linear coupling can compensate for the group delay between eigenmodes and cause energy fluctuation between modes which weakens the nonlinear effects. In high energy pulses, the interaction of linear coupling and nonlinear effects can help producing weak dispersion waves when the spectrum is broadened. Since linear coupling in a mode group is common and unavoidable, these results may provide a certain theoretical explanation for multi-mode nonlinear phenomena.     

时间拉伸色散傅里叶变换在被动锁模光纤激光器研究中的应用

时间拉伸色散傅里叶变换(TS-DFT)技术推动了锁模激光器中瞬态现象的研究,对于揭示复杂系统中的耗散动力学过程具有重要意义。介绍了TS-DFT技术的基本原理及其在数据采集和数据处理中存在的关键问题,总结了TS-DFT技术在被动锁模光纤激光器的类噪声脉冲与怪波、孤子爆炸、孤子束缚态、锁模自启动和矢量孤子等各类超快现象研究中的应用。     

紧凑型光谱组束系统中光纤阵列扰动对光束质量的影响分析

定量分析光纤阵列位移及指向扰动偏差对合束激光光束质量因子M²的影响规律是实现合束激光光束质量有效控制的前提。根据衍射积分推导了紧凑型光谱组束系统中光纤阵列存在不同位移、指向扰动时合束激光的远场光强分布,利用Heisenberg不确定性原理推导出了合束激光光束质量因子M²的表达式。在恒定的子束数目下,分析了单路/多路光束分别存在位移、指向扰动偏差时合束激光光束质量因子M²的变化情况,并在一定的随机位移、指向扰动偏差下对不同子束数量的合束激光的光束质量因子M²进行了误差分析。结果显示：合束激光光束质量因子M²对沿光纤端面水平(x轴)方向的扰动量最为敏感,需要控制在微米量级;确定了光纤阵列的不同扰动量与合束激光光束质量因子M²之间的定量关系,给出了光纤阵列位移、指向精度控制要求;当参与合束的子束数量超过23束时,在特定的随机扰动量下,合束激光的光束质量因子M²的统计均值分别趋向各自的稳定值1.37、1.34、1.25,而标准差分别趋于0.0...