Study On The Seed Source Of Thulium-doped Fiber Laser With Continuous And Pulse Switchability

The output laser of thulium-doped fiber laser is located in 2?m band,which is located in the low loss window of atmospheric optical transmission.Therefore,thulium-doped fiber laser has been paid more and more attention in the field of remote sensing and optical communication.It is the first choice of light source for laser rangefinder,coherent Doppler wind radar and lidar system.There is a strong OH-absorption window in this band.The thermal effect of laser can make human tissue vaporize and produce coagulation effect.Therefore,it can be used as a scalpel in laser medicine.It can effectively avoid the shadow caused by too many bubbles,tissue fragments and colored laser protective glasses.It has the advantages of keeping the endoscope lens clear and tidy when performing laparoscopic examination in the air.According to different surgical requirements,laser scalpel should be switched between continuous wave and pulse.Because of the subjectivity and security of the application scenario,this paper proposes that in the thulium-doped fiber laser seed source system,using acousto-optic Q-switching mode to switch between two kinds of lasers,that is,adding acousto-optic Q-switching switch in the resonant cavity of thulium-doped fiber laser,by setting the parameters of repetition frequency and opening time reasonably,to output high quality pulses that meet different requirements.For the switching between CW output and pulse output of thulium-doped fiber laser,the work done in this paper is as follows:(1)A theoretical model of Q-switching for 2?m band thulium-doped fiber laser is established.The formation process of pulse in Q-process is analyzed,and the expressions of pulse width,output power and energy are obtained;(2)The effects of pump power,Q-switching repetition frequency and resonant cavity length on pulse width,repetition frequency and peak power are simulated and analyzed,and the method of optimizing pulse waveform is obtained;(3)An experimental system of acousto-optic Q-switched thulium-doped pulsed fiber laser is established.At low repetition frequency,the output pulse is continuously adjustable at 1?100Hz.At high repetition frequency,the pulse width is 190 ns and the output power is 3.632 mW under the condition of 2W pump power and 20 kHz repetition frequency;...