Research On High-power And High-energy All Polarization-maintaining Fiber Femtosecond Laser And Amplifier

This dissertation mainly studies the technology of high-power and high-energy femtosecond fiber laser and the technology of high-power and high-energy femtosecond fiber amplifiers.Starting from the principle,this dissertation studies the generation of femtosecond pulses and the transmission characteristics of femtosecond pulses in fibers and then constructs a model consistent with the experimental results to simulate and qualitatively describe the generation and transmission of femtosecond pulses in fiber lasers.Based on the understanding of femtosecond fiber lasers,a set of high-power and high-energy all-polarization-maintaining-fiber-structure soliton-mode-locking fiber laser,and an all-polarization-maintaining-constructed femtosecond laser source for coherent anti-Stokes Raman scattering(CARS)spectroscopy technology are designed and implemented.The former has the potential to improve the system stability of the latter.Finally,a set of cascaded high-power and high-energy all-polarization-maintaining-fiber-structure ytterbium-doped femtosecond laser fiber amplification system with variable repetition frequency is realized.The detailed results are listed as follows:(1)Master the common mode-locking technology of fiber lasers.Based on the understanding of dispersion,nonlinear effects,and gain,a model of a hybrid mode-locked structure including a semiconductor saturable absorption mirror(SESAM)and a nonlinear amplifying loop mirror(NALM)is established,and the self-starting characteristic corresponding to the experiment is realized from the simulation.Popularizing the basic principles of this model can provide visual theoretical guidance for studying femtosecond pulse mode-locking and the transmission characteristics of femtosecond pulses in fiber lasers.(2)Improving the NALM structure based on the understanding of the soliton area theory.By strictly controlling the nonlinear phase shift difference in the NALM while providing sufficient gain to shorten the evolution distance of the soliton,the transform-limited soliton with single pulse energy of 1.19n J is achieved in the all-polarization-maintaining-fiber-structure erbium-doped fiber laser.(3)Based on self-similar amplification and supercontinuum broadening,an all-polarization-maintaining-fiber-structure femtosecond fiber laser source for coherent anti-Stokes Raman scattering(CARS)spectroscopy technology is realized,which can provide a detection bandwidth of more than 4000 cm^-1 and the detection resolution of24cm^-1.(4)Combining chirped pulse amplification(CPA),self-similar amplification,and photonic crystal fiber(PCF)to establish a cascaded high-power and high-energy all-polarization-maintaining-constructed ytterbium-doped femtosecond laser fiber amplification system.The acousto-optic modulator(AOM)is used to synchronously change the repetition frequency,and finally,the output pulses with adjustable repetition frequency,average power exceeding 40W,single pulse energy up to 200?J,and the compressed pulse duration less than 350fs are realized.