少模液芯光子晶体光纤中飞秒脉冲的演化研究

本文旨在研究少模光纤中飞秒脉冲的传输与演化特性。提出了一种高非线性少模甲苯液芯光子晶体光纤(Toluene Liquid-Core Photonic Crystal Fiber, TLC-PCF)。泵浦波长处的非线性系数约为 42 W^-1·km^-1。采用多模广义非线性薛定谔方程(MM-GNLSE)对飞秒脉冲的传输与演化进行了建模和求解。对比了不同峰值功率(1 kW、10 kW、50 kW)的能量转移特性。当中心波长为2000 nm、峰值功率为50 kW、脉宽为200 fs的高斯脉冲在30 cm长的TLC-PCF中传输时，得到1980～2500 nm的超连续谱输出，能量转移在0.02 m处首次到达平衡点。数值结果表明，当一个模式被激发时，其简并模式会发生能量转移，且四波混频(Four-Wave Mixing, FWM)负责TLC-PCF中模式间的能量转移。本文创新性地采用MM-GNLSE理论分析具有慢非线性的少模液芯光子晶体光纤中的模式耦合、超连续谱产生(Supercontinuum Generation, SCG)以及能量转移特性。

Research on The Evolution of Femtosecond Pulses in Few-Mode Liquid-Core Photonic Crystal Fibers

In this paper, we aim to study the transmission and evolution characteristics of femtosecond pulses in low-mode fibers. A kind of high nonlinear few-mode toluene liquid-core photonic crystal fiber (TLC-PCF) is proposed. The nonlinear coefficient at the pump wavelength is about 42 W^-1·km^-1. MM-GNLSE is used to model and solve the femtosecond pulse transmission and evolution. The energy transfer characteristics of different peak power (1 kW, 10 kW, 50 kW) are compared in this paper. When a Gaussian pulse with a central wavelength of 2000 nm, a peak power of 50 kW and a pulse width of 200 fs is transmitted in a TLC-PCF with a length of 30 cm, the supercontinuum output of 1980－2500 nm is obtained, and the energy transfer reaches the equilibrium point for the first time at 0.02 m. The numerical results show that the energy transfer occurs in degenerate modes when a mode is excited, and it is concluded that four-wave mixing (FWM) is responsible for energy transfer between modes in TLC-PCF. In this paper, MM-GNLSE theory is innovatively adopted to analyze mode coupling, SCG and energy transfer properties in a few mode liquid-core photonic crystal fiber with slow nonlinearity.