少模液芯光子晶体光纤中飞秒脉冲的演化研究

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

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(Multimode Generalized Nonlinear Schr9dinger Equation,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。

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.