Study On High-power High-quality All-fiber Femtosecond Laser Amplification System

The Yb-doped large mode area polarization maintaining double-clad fiber(PLMA-YDCF)can offer the advantages of the large core diameter,robust polarization preserving characteristics,and accessibility of low loss fusion splicing with other fibers,which make them ideal gain medium for all-fiber femtosecond laser system.A fiber chirped-pulse-amplification(FCPA)system could benefit from the all fiber features and scale up the output power of the fiber lasers.In this thesis,in order to build up a high-pulse-quality,high-power,good-stability femtosecond fiber chirped-pulse-amplification(FCPA)system,the double-clad Yb-doped fiber and the negative third-order dispersion fiber(NTF)are utilized as gain medium and fiber stretcher,respectively.Compensation of third-order dispersion in a fiber pulse chirped amplification system is studied both in our numerically and experimentally.The NTF is implemented to compensate the mismatched third order dispersion,resulting a high-pulse-quality output.What's more,we investigate some key elements of the fusing and the thermal management of the laser system.And finally,we present a concept of a prototype design of high-power all-fiber femtosecond laser amplification system.The dissertation can be summarized as bellow:1.A numerical model of chirped pulse amplification basing on the nonlinear Schrodinger equations and rate equations is constructed.Using the split-step Fourier method,the effects of three-order dispersion on pulse temporal profile is studied and numerically analyzed.According to the analysis,the compensation of the residual third order dispersion will improve the output pulse quality.2.Based on the FCPA technique,we build up an all-fiber femtosecond laser system,which incorporate a newly developed stretcher fiber to compensate the third order dispersion(TOD)of laser system.With the help of NTF,the dispersion of the fiber stretcher well matches that of grating compressor.Consequently,we obtain a high quality dechirped pulse with central wavelength of 1035 nm and pulse duration of 217 fs.In addition,average output power of 8.5 W at repetition rate of 111 MHz is achieved.3.We explore the key processes and technologies to build a high power femtosecond fiber laser system,including some key elements of the fusing,design of the endcap output and the thermal management of the laser system.Based on our investigation,we present a prototype design of high-power all-fiber femtosecond laser amplification system.