Experimental Study On Output Characteristics Of Tm-doped Mode-locked Fiber Laser

Fiber laser has been developed rapidly in recent years,and it is a kind of laser that uses rare earth elements-doped fiber as the gain medium.Its working principle is the same as that of traditional solid laser.But,compared with solid state lasers,there are many advantages,such as better stability,less maintenance,more compact structure,less thermal effect,lower threshold power and higher conversion efficiency.The laser with a wavelength of 2 ?m is in the eye-safe waveband.Moreover,2?m laser has low loss in the atmosphere,because it is in the atmospheric window.Therefore,it has broad application prospects in lidar,remote sensing,medical and industrial processing.Thulium doped fiber laser at 2 ?m has very rich research value.Nowadays,many famous laser laboratories in the world have carried out research in this direction.Mode-locked fiber laser can generate higher peak power and different form of pulse train.Therefore,compared with continuous wave fiber laser,mode-locked fiber laser can be applied widely in many fields.In mode-locked fiber laser with thulium doped,the kinds of Tm-doped fiber and passive fiber,pump power,laser mode locking mechanism,and the resonant cavity structure will have a certain impact on the output characteristics,which will limit the development and application of 2 ?m Tm-doped fiber laser,so it is necessary to investigate the influence of different factors on the mode-locked Tm-doped fiber laser output performances.In the thesis,the experimental research of Tm fiber laser is carried out,which includes pulse-splitting and pulse-broadening.In pulse-splitting part,we vary the polarization state of the laser in the resonant cavity and the pump power of thulium doped fiber laser to achieve different pulse clusters and harmonic pulse output,and summarizes the influences of pump power and polarization state on pulse-splitting.In pulse-broadening part,we get many kinds of pulse trains with different pulse width by changing the pump power and the polarization state,and summarize the influence of polarization state and pump power on the output pulse width.