Research On Chirped Pulse Amplification Of KHz Femtosecond Laser

High average power femtosecond laser has important application value in scientific research,biomedicine,communication,material processing and so on,and has gained high speed under this demand.Solid-state femtosecond laser amplifiers based on chirped pulse amplification technology have the advantages of stable performance,high peak power,broad spectral composition,and good beam quality,and thus have received widespread attention.In this dissertation,relevant theoretical simulations and experimental studies are carried out around dispersion management,thermal control and energy amplification in chirped pulse amplification system,The main research works and the innovative results are summarized as follows.1.The pulse width stretching and compression in chirped pulse amplification are systematically studied and analyzed.Starting from the basic theory of dispersion in femtosecond optics,we have analysed the dispersion of common media materials in CPA systems,and used the ray-tracing method to calculate the optical path length of prism compressor,Martinez stretcher and grating pair compressor to obtain the analytical equation of dispersion.It provides theoretical guidance for the dispersion management in the whole CPA system.2.The types of common femtosecond laser amplifiers are classified and described,and the advantages and disadvantages of several typical amplification structures are compared in detail.The process of ultrafast laser regenerative amplification has a complex dynamic behavior,based on the improved Frantz-Nodvik equation,the output behaviors of the regenerative amplifier with different repetition rates are simulated.Based on theoretical analysis,the regenerative amplifier was constructed and the laser amplification results were realized with pulse energy of 1 mJ at a repetition rate of 1 kHz.The experimental results agree well with the theoretical analysis above.The influences of the injected into pulse energy,the loss coefficient a and the initial energy storage density on the establishment time and efficiency of the regenerative cavity were further simulated,and the thermal effect in the amplification was analyzed and calculated,which has reference significance for the subsequent research on energy amplification.3.Considering the effect of thermal lens effect on the mode operation in the regenerative amplifier cavity,we designed and built a thermally insensitive regenerative cavity,which can meet the high power amplified laser output.The amplified laser output with an average power of 5.6 W was obtained under 20 W,5 kHz 527 nm laser pumping.Based on the study of the high power regenerative amplifier,we designed and built a one-stage four-pass power main amplifier.Pumped by 40 W,5 kHz 527 nm laser,using dual TEC and water-cooled cooling scheme to cool the crystal to 233 K to alleviate the thermal lens effect,and the amplified laser was compressed by a single grating compressor to achieve femtosecond laser output with an average power of 7.5 W,pulse width as short as 28 fs at repetition rate of 5kHz.Based on this study,an integrated engineering prototype of a femtosecond laser amplifier was developed,and the measured power stability RMS of the prototype is less than1%,which can be used by users for experimental research.