Repetitive Frequency Locking And Noise Analysis Of Erbium-doped Fiber Laser

Femtosecond optical frequency comb is further important breakthrough in the field of laser technology after the advent of ultrashort pulse laser.It is a new type of laser sources with ultrashort pulses(femtosecond),which are produced by mode-locked lasers.If the repetition frequency and carrier-envelope phase shift of femtosecond laser pulses can be precisely controlled,according to Fourier transform,a series of comb shaped frequency lines with uniform distribution,fixed position and extremely wide spectral range in the frequency domain can be obtained,called"optical frequency comb".Mode-locking methods of fiber lasers can be sorted into two types:active mode-locking and passive mode-locking.This thesis discussed the passive mode-locking mode.The main types of passive mode-locking include the use of semiconductor saturable absorber mirrors(SESAM),nonlinear polarization rotation(NPR)effect and nonlinear optical loop mirror(NOLM).In this thesis,the nonlinear polarization rotation(NPR)passive mode-locking technique was selected to lock an erbium-doped fiber laser,and the stability of the repetition rate was tested.The result showed that stability was 1.21×10^-13 at one second gate time.The dispersion of fiber is very important to the operation of femtosecond lasers,which mainly includes material dispersion and waveguide dispersion.The dispersion compensation can control the dispersion and get the desired results.In the process of designing erbium-doped fiber lasers in this project,we also encountered that the control of total dispersion and gain in the cavity was not precise enough,which caused the erbium-doped fiber lasers not to be mode-locked.Finally,after our careful investigation,we successfully obtained the mode locking of the erbium-doped fiber laser.The relative intensity noise(RIN)of a laser is an important index to evaluate the performance of it.Based on the erbium-doped fiber laser built in the laboratory,the scheme of measuring the RIN was given,and the result was less than 0.09%.