Study On Generation And Squeezing Of Self-similar Pulses In Photonic Crystal Fiber

With the increasing application of ultra-short optical pulses in communication,medicine,aerospace,military and other fields,people have higher requirements for their peak power and width.Therefore,the technology of generating ultra-short optical pulses is becoming increasingly important.Pulse compression technology is one of many methods for obtaining ultra-short pulses.Pulse compression technology needs to widely use the linear and non-linear characteristics of transmission fibers,but ordinary fibers can't be widely used because of their poor performance,while photonic crystal fibers can be designed according to people's needs due to their structural characteristics,which can overcome the above defects,and Compared with optical fiber,it has more excellent dispersion,linear and non-linear characteristics,which makes it have a wide range of application prospects in optical pulse compression and other fields.Self-similar pulses are generated in dispersion-decreasing photonic crystal fibers and the normal dispersion region of fiber amplifiers.Because of their strict linear chirp characteristics,they are widely used for compression to obtain high-power ultra-short pulses.Self-similar pulses can suppress light wave splitting and have self-similar characteristics in pulse shape,self-similar characteristics are only related to the initial incident pulse energy and fiber parameters,and have nothing to do with the initial incident pulse shape,so people have been doing many studies about it.Firstly,this article introduces the characteristics of photonic crystal fibers,the basic theory of light pulse transmission in photonic crystal fibers,the formation of self-similar pulses,and the basic principles of compressing pulses to obtain ultra-short pulses.Taking Maxwell's equations as the starting point for the discussion,a series of calculations are performed to obtain the wave equation of pulse transmission,and the nonlinear Schr?dinger equation(NLSE)that the light pulse is transmitted through the fiber is further deduced.Aiming at this equation,a numerical simulation method of light pulse compression mining—symmetry split-step Fourier method(SSFM)is given.Secondly,the effects of initial pulse waveform,initial pulse peak power,pulse width,and high-order dispersion on the evolution of self-similar pulses are analyzed using MATLAB software.Then the transmission evolution characteristics of self-similar pulse pairs in optical fiber are studied.Finally,introducing the pulse compression method and a linear combined with on-linear optical fiber cascaded pulse compression method is proposed for the above optimal self-similar pulses.A section of high-dispersion photonic crystal fiber is designed for compression,whose feasibility is verified by COMSOL and MATLAB software.