Research On Self-similar Pulse Propagation In Laser System And Design Of Compression System

With the in-depth application of ultrashort pulses in industrial production,information acquisition,biomedicine,information transmission and storage,how to obtain ultrashort pulses with higher power,shorter pulse width and no pedestal has become the focus of scholars at home and abroad.Research hotspots.Among them,the self-similar pulse has the advantages of good linear chirping,keeping the time-domain waveform unchanged during transmission,and avoiding light wave splitting during high-power transmission,so that the pulse can be compensated by chirping.Pulse attracted people's attention.How to obtain a stable and highquality self-similar pulsed light source and how to effectively chirp compensation for the selfsimilar pulses have become the key issues to generate high-power ultrashort pulses based on self-similar pulses.It is under this background that this thesis proposes the transmission research and compression system design of self-similar pulsed fiber lasers.By establishing the numerical model of self-similar mode-locked fiber lasers,the evolution and transmission characteristics of self-similar pulses in fiber lasers are analyzed and simulated.,the selfsimilar pulse mode-locked pulse output with better quality and higher peak energy is obtained by optimizing the system parameters and structure,and the self-similar pulse is compressed by the compensation fiber and grating through the chirp compensation effect.short pulse.The main research contents and research results of this thesis are summarized as follows:(1)By simplifying Maxwell's equations,the basic equation of optical pulse transmission in optical fiber-nonlinear Schr(?)dinger equation is obtained.On the basis of nonlinear Schrodinger equation,the influence of dispersion effect and nonlinear effect in optical fiber on pulse time-domain waveform and frequency spectrum is analyzed.(2)The numerical analysis model of self-similar pulse mode-locked fiber laser is established by distributed method according to the mode-locking theory.The effects of gain saturation energy,intracavity net dispersion,and modulation depth of saturable absorber on the peak power,full width at half maximum,energy,and self-similar coefficient parameters of mode-locked self-similar pulses in lasers are studied.The research shows that,within a certain range,increasing the modulation depth of the saturable absorber can improve the quality of the self-similar mode-locked pulse,and also increase the pulse energy without distortion.Inspired by this,we optimized the laser by adjusting the parameters and the number of saturable absorbers.Using two saturable absorbers with a modulation depth of 0.55,a selfsimilar pulse with a smaller self-similar coefficient and a higher peak power was obtained.Output,and complete the construction of self-similar mode-locked fiber laser system through Opti System software.(3)Compensation and compression of self-similar pulses by using dispersion compensation fiber and grating pair by chirp compensation effect,and by changing the dispersion change function,the effects of common dispersion compensation fiber,dispersion increasing compensation fiber,and dispersion decreasing compensation fiber on self-similar pulse compression characteristics are studied.The research shows that: Compared with the common dispersion compensation fiber,the dispersion reduction compensation fiber can obtain ultrashort pulses with larger compression factor and higher peak power,and the pulse width of the ultrashort pulse can be further reduced by reducing the dispersion reduction coefficient.and increased peak power.Finally,the design of the self-similar pulse compression system is completed by Opti System software.