The Experiment Research About Femtosecond Fiber Laser Locked To Ultra-narrow Linewidth Laser

Measurement of the fundamental physical quantities plays a very important role in basic physics researches and applications.The optical frequency standards system includes ultra stable laser, ion trap and optical frequency comb.To meet the need of the aluminum ion optical frequency standard group’s research, the main task of my research is to realize the phase locking of the femtosecond comb locked to an ultra-narrow linewidth laser.In order to fully understand the femtosecond comb in theory,the author briefly presents the generation of the femtosecond comb, mode-locking process and the methods of detection the two key parameters fo and fn Using the MeoloSystems’ femtosecond comb in our laboratory, we measure the optical linewidth,the optical spectrum and the control loop of the comb. Then we make use of this powerful system to measure the frequency stability of an1068nm ultra-narrow linewidth laser and give the detail process about how to calculate the laser’ absolute frequency value, and then compared with the result given by a high precision wavemeter.In addition, we measure the frequency stability of the magnesium ions cooling laser.About the phase locking scheme for femtosecond comb to the ultra-narrow linewidth laser,we obtain a high signal to noise ratio beat note for locking and use a home-made digital phase detector to lock the offset beat frequency.The achieved frequency stability is1.3×10-7@ls.After we achieve the locking between the femtosecond comb and the ultra-narrow linewidth laser successfully, we obtain a in-loop the frequency stability of5.7x10-15@1s In comparison, If the comb is locked to a Hydrogen maser the frequency stability is2.5×10-13@ls.Using the timestamp frequency measurement method, we compare the Allan deviation at the microsecond range when the comb is locked to Hydrogen maser,Cs clock and the ultra-narrow linewidth laser. Finally,we use the phase noise analyzer to compare the comb’s RPEetition rate result when the comb is locked to Hydrogen maser and1068nm ultra-narrow linewidth laser.