基于零模间色散双芯光子晶体光纤的飞秒脉冲全光孤子开关研究

As a current research focus in the area of all-optical communication, the dual-core photonic crystal fiber (PCF) has important applications in the fiber directional coupler and all-optical switching because of its unique characteristics such as the design flexibility, endless single mode, controllable dispersion and nonlinearity, which are not enjoyed by the conventional fibers. This project is devoted to a theoretical study on the all-optical soliton switching of femtosecond pulses in the dual-core PCF with zero intermodal dispersion. First, we design the dual-core PCF with zero intermodal dispersion to avoid the pulse distortion, and derive the physical model for the femtosecond pulse propagation in the dual-core PCF with the consideration of such effects as higher-order dispersion, self-steepening and stimulated Raman scattering. Also, the analytical vector-soliton solutions are constructed for such physical model. Second, we study the mechanism of realizing the all-optical soliton switching of femtosecond pulses based on the energy-exchanging collisions of vector solitons, and obtain the parametric conditions that the input pulses and related physical quantities should meet. Third, we perform the linear stability analysis on the modulation instability of femtosecond pulses, and further analyze the influence of the input pulse power, coupling strength and initial perturbation on the performance and stability of the all-optical soliton switching via the numerical simulation. This study will advance the development of the all-optical switching technology with large capacity, high switching speed, low loss and high reliability.

双芯光子晶体光纤(PCF)是当前全光通信领域的研究热点之一，它具有传统双芯光纤无法比拟的设计灵活性、无截止单模性以及可控的色散和非线性等优点，在光纤定向耦合器以及全光开关方面有着重要应用。本项目致力于在零模间色散条件下对双芯PCF中飞秒脉冲全光孤子开关理论进行研究。首先，设计可实现孤子脉冲无畸变传输的零模间色散双芯PCF结构，并考虑高阶色散、自陡峭以及受激拉曼散射等高阶效应的影响，建立模拟双芯PCF中飞秒脉冲传输的物理模型，进而利用解析方法构造所得模型的矢量孤子解。其次，根据矢量孤子能量交换碰撞的性质建立飞秒脉冲全光孤子开关的实现机制，同时给出入射脉冲与各物理量应满足的参数条件。第三，通过线性稳定性分析研究飞秒脉冲的调制不稳定性，并借助数值模拟分析入射脉冲功率、耦合强度以及初始微扰等因素对开关转换性能及稳定性的影响。本研究将有助于推动大容量、高交换速度、低损耗和高可靠性全光开关技术的发展。

本项目致力于研究零模间色散条件下双芯光子晶体光纤中飞秒脉冲的传输特性及全光孤子开关理论，主要研究内容及成果如下：（1）研究了双芯光子晶体光纤中若干耦合系统的矢量光脉冲——借助广义达布变换方法求得了混合耦合非线性薛定谔（NLS）模型的退化和非退化的矢量怪波解，分析了怪波的动力学演化性质。（2）研究了具有PT对称结构的光子晶体光纤中非局域NLS模型的解析解——通过渐近分析方法揭示了自聚焦和自散焦情形下的孤子碰撞类型以及PT对称平移对孤子解稳定性的影响；基于离散的PT对称非局域NLS模型，构造了离散的呼吸子解、周期波解和有理孤子解，讨论了有理孤子的碰撞性质。（3）研究了在高阶非线性效应下光子晶体光纤中飞秒脉冲的局域波现象——以带有周期外部扰动的广义高阶NLS模型为基础，讨论了无扰动情形下产生同宿轨道和异宿轨道的参数条件，以及周期性扰动下的拟周期分叉和混沌演变现象；以平面波为背景求得了广义高阶NLS模型的三种非线性波解，讨论了孤子和呼吸子之间以及怪波和非线性波之间的碰撞特性。（4）研究了非均匀光子晶体光纤中变系数非线性发展模型的非线性波——基于变系数共振NLS模型推导出了四种非自治孤子解，并讨论了非自治孤子的非均匀传播效应和相互碰撞性质；基于带有高阶效应的变系数NLS方程分析了非自治呼吸子和非自治多峰孤子之间的转换。（5）研究了光波导阵列中离散NLS模型的高阶呼吸子解及怪波形成机制——揭示了不同参数条件下的呼吸子类型以及呼吸子-呼吸子、呼吸子-怪波的相互作用；以新的平面波为背景求得一阶呼吸子解，并通过分析群速度和相速度的准确表达式，找到了速度产生跳跃的参数条件，进而揭示怪波的形成机制。