Theoretical, Experimental And Driving Source Research For Spectral Filtering

Ultrafast fiber lasers have developed rapidly in recent years and are widely used in optical communications,medical,materials processing,radar,science and other fields.Due to the bandwidth limitation of gain doped ions,the operating bands of ultrafast fiber lasers are mainly concentrated around 1 μm,1.5 μm and 2 μm,however,many applications urgently require high-energy femtosecond pulses with wavelengths tunable over a wide range,and cannot be directly provided by ultrafast fiber lasers.The rapid development of self-phase modulated enabled spectral selection(SESS)in recent years can meet the needs of such applications,although the analytical theory of this technique is not yet well studied to provide precise guidance for experiments.On the experimental side,group velocity dispersion(GVD)in optical fibers deteriorates the spectral broadening process and degrades the quality of SESS light sources,while there is also an urgent need to develop femtosecond pumped light sources capable of generating SESS pulses of microfocal magnitude.To address these issues,this thesis focuses on the theoretical,experimental,and high-power sources for SESS technology.The thesis develops the analytical solution of the nonlinear Schr(?)dinger equation with self-phase modulation(SPM)and GVD terms;secondly,the dispersion management SESS technique is proposed to realize the regulation of the spectral broadening process;finally,based on the split-pulse amplification technique and chirped-pulse amplification technique,a high-power,high-energy SESSdriven light source is obtained.The specific research contents and innovation points of this thesis are as follows:1.Perfecting the analytical solution of the nonlinear Schr(?)dinger equation.The improved analytical solution can effectively describe the spectral broadening process of Gaussian pulses or hyperbolic positive cut pulses in fibers with positive or negative GVD in the presence of SPM and GVD simultaneously.Compared with other current theories combining SPM and GVD,our theory can better fit the simulation results and provide more accurate theoretical guidance for experiments.2.Experimental study of SESS based on dispersion management techniques.Dispersion in optical fibers can reduce the clarity of the spreading spectral partials,while light wave splitting effects can also occur when pulses evolve in positive-dispersion fibers,further affecting the spectral spreading width.Based on this,we proposed the first experimental scheme of SESS based on dispersion management by combining doublepass structure with chirped mirror or using dispersion alternating fibers fused to each other,and both simulation and experimental results proved the feasibility and advantages of this scheme.3.Research on high-energy and high-power SESS driving sources based on dividedpulse and chirped-pulse amplification.We use two techniques of divided-pulse amplification and chirped-pulse amplification to develop a high-energy,high-power SESS driving source.In the divided-pulse amplification experiments,146 fs ultra-short pulses with a pulse energy of 8 μJ and an average power of 8 W were successfully obtained.Using the chirped pulse amplification technique and a two-pass amplifier based on a rod fiber as the front-end,stable pulses with a single pulse energy of 180 μJ,an average power of 180 W,and a pulse width of 242 fs were successfully obtained.These sources will be used for subsequent SESS experiments based on hollow-core fiber or multi-pass cell broadening spectra.