Impact Of Higher-order Nonlinear Effects On The Chirped Soliton-like Pulses

Based on the higher-order complex Ginzburg-Landau equation, which is used to describe the evolution of ultrashort optical pulses in the mode-locked laser systems, the chirped soliton-like solution is studied in detail by using both the analytic method and the numerical simulation method. When the width of the pulse is femtosecond and even attosecond, it is necessary to study the impact of higher-order nonlinear effects on the pulse transmission. The results will provide some theoretical references for obtaining even higher energy and shorter width pulse.The main works of this paper is arranged as followed. Firstly, the chirped soliton-like solution is presented based on the theoretical model of the mode-locked laser systems. And the impaction of the nonlinear-delayed effect on the solution is analyzed in detail. The results are verified by using numerical simulation methods. Though the system exist some perturbations, the chirped soliton-like solution can be transmitting stably. Even when the initial pulse is a random Gauss pulse or hyperbolic secant pulse, the exact solution is formed after a certain distance of transmitting. Secondly, the impact of the fourth-order dispersion on the laser system solution is studied. The results show that the fourth-order dispersion has very obvious influence on the evolution of the chirped soliton-like solution. The solution is unstable when the fourth-order dispersion is taken into account and the soliton will split into several pulses after a definite distance.The paper is constituted of five chapters. Chapter one is the introduction, chapter2shows the basic theory of this paper, and the chapter3and4are the main works of this paper. Chapter5makes a summary of the whole paper. The main contents are as follows:Chapter1introduces the fiber communication research status and application prospect. The main work of this paper is also introduced briefly.Chapter2shows the theoretical basis of this paper: the pulse transmission equation in fiber and relevant numerical simulation method. Chapter3presents the higher-order nonlinear complex G-L equation including nonlinear delayed effect. And the exact chirped soliton-like solution is got. The stability of the chirped soliton-like solution is studied by variational method and Distribution Fourier Transform. The evolution of soliton-like solution under some perturbations is analyzed with numerical simulations.The nonlinear complex G-L equation including the fourth-order dispersion is solved in Chapter4. Using anastz method, the chirped soliton-like solution is got. The impact of fourth-order dispersion on the solution’s parameters is analysised.Chapter5is the conclusion of the paper.