Theoretical Simulation Of Supercontinuum Generation By Pumping Long And Short Pulsed Laser At Different Dispersion Zones

Supercontinuum(SC)light source has the advantages of high energy,wide spectrum,strong spatial coherence,etc.It is a good choice to replace the existing broad band light source of Superluminescent Diode(SLD).High peak power,high beam quality and miniaturized SC light sources have become important research directions.In this paper,we adopted the Nonlinear Schrodinger Equation(NLSE)and the Generalized Nonlinear Schrodinger Equation(GNLSE)under single-mode conditions through the Maxwell equation.Then the material dispersion curves of SC-5.0-1040 optical fibers(Photonic Crystal Fiber,PCF)and SMF-28 optical fibers are calculated with the Sellmeier equations.The cross section of the optical fibers is analyzed by the finite element analysis method with the Mode-Solution software,and the effective refractive index curves of the two optical fibers are calculated,and the waveguide dispersion curves are obtained by the inverse analysis.The 10th order numerical solution of the optical fiber propagation constants,?,at the center wavelength of the pump light are obtained by using MATLAB,and the basic parameters of the optical fiber required for the numerical solution of SC are obtained.The research on broadband SC is focused on femtosecond mode-locked laser pumped PCF,so the numerical calculation of SC is also focused on abnormal dispersion zone of short-pulse pumped optical fiber.However,the shortcomings of this SC light source,such as high cost,complex structure and difficulty to carry,limit its application in life scenes.By contrast,compact solid-state lasers with high peak power and high beam quality are more likely to become pumping sources for commercial SC light sources.Because the main non-linear effects in different dispersion zones of different pulse width pumped optical fibers are different,different numerical models are used to simulate the nearzero dispersion point(ZDW)and normal dispersion zone of short and long pulses pumped optical fibers respectively in SC numerical calculation,and the corresponding frequency-domain broadening are obtained by using RK4IP.Finally,a high performance passively Q-switch microchip laser was constructed experimentally using Yb:YAG laser crystal as gain medium and Cr4+:YAG passively Q-switched crystal as saturable absorber.By using this Yb:YAG/Cr4+:YAG passively Q-switched laser as pump source,a broadband supercontinuum light has been generated in a SMF-28 optical single-mode fiber.The theoretically calculated results are in fair good agreement with the experimental results.Therefore,the results of this study can provide theoretical and simulation basis for the future experiments on the generation of supercontinuum spectrum in short-pulse and long-pulse-pumped optical fibers.