Research On All Polarization-maintaining Femtosecond Fiber Laser With High Stability

Ultrashort-pulse laser has characteristics such as narrow time-domain width,wide spectrum and extraordinarily high peak power,and plays an important role in the researches on ultrafast process.As a high-end technology,ultrashort-pulse laser has also been widely applied in the industrial field.Compared with the lasers with other gain mediums,the fiber laser has excellent beam quality,higher level of integration,and easy maintenance.All make femtosecond fiber laser to be an important laser technology.In the research of femtosecond fiber laser,the mode-locking technology,a hot topic,is the key to ensuring the stability of the femtosecond lasers,and is also one of the focuses of the research on femtosecond laser technology.This thesis focuses on the all polarization maintaining mode-locked fiber laser.and studies the tunability and stability of the repetition rate.A mode-locked fiber laser based on dispersion-managed soliton is developed It outputs stable pulse train with several hundreds of femtoseconds pulse duration by optimizing the dispersion compensation and net dispersion in the cavity.Meanwhile,a mode-locked fiber laser with a repetition rate tuning ratio of 23%is developed utilizing a specially designed optical delay line.In order to apply the laser outside labs,a special structure is designed,and the temperature stability test is carried out.Finally,the repetition rate is successfully locked on the reference frequency based on Rb atomic clock.The main contents of this thesis are summarized as below:1.The mechanism of pulse evolution in fiber mode-locked laser is analyzed.A model is established for simulation of the formation and evolution of ultrashort laser pulse,and solved by numerical method.With the help of this model,the fiber parameters of the mode-locked fiber laser are optimized.2.An all fiber femtosecond mode-locked laser based on dispersion-managed soliton is developed,and the repetition rate tuning in a range of 6 MHz is realized utilizing optical delay line.The effects of CFBG's dispersion compensation and net cavity dispersion on the output spectrum and stability of the mode-locked laser are studied,and stable output with near Gaussian spectrum is obtained.Based on the result above,the maximum repetition rate tuning rage under different net cavity dispersion is studied.The pulse train with tunable repetition rate around 26 MHz is realized,with a tuning ratio of 23%.3.A compact anti-interference mechanical structure is designed for the laser.The integrated laser is tested in alternating temperature test chamber under a wide temperature range.In the testing time of 25000 s,the output power has good repeatability,with a relative change of repetition rate less than 0.07%.The repetition rate of mode-locked laser is then locked on the reference frequency based on Rb atomic clock,and the repetition rate drift is reduced from 62 Hz to 0.85 Hz in 10000-s testing time,with the Allen variance of 2×10^-10 when average time is 1 s.The stability of output repetition rate of the laser is significantly enhanced.