Experimental Study On 2μm Band Free-isolator Thulium-doped Fiber Laser

In recent years,fiber lasers have received wide attention from industry and academia due to their compact structure and high beam quality.Among them,Tm-doped fiber lasers have great potential for application in biomedicine such as medical scalpels and tissue cutting by virtue of their ability to produce lasers with safe wavelengths for human eyes.However,due to the speciality of the 2 micron band and the immature technology,the 2 micron band devices are expensive,which greatly limits the research and application of erbium-doped fiber lasers.The main work of this paper is as follows:1.In this paper,the energy level structure of the erbium ion,the pumping method,and the-pumping method are theoretically modeled,and the rate equation is derived.Finally,the equation is solved by MATLAB syms function,and the simulation experiment is carried out.The influence of the concentration of doping ions and the length of the fiber on the erbium-doped fiber laser is discussed.The influence of the cross-relaxation phenomenon on the absorption performance of the erbium-doped fiber is analyzed,and the erbium-doped fiber is obtained when the doping concentration is5.6×10²⁴m^-3,The optimum length is 14 meters,at which time the pump light can be fully absorbed,so that the output performance of the erbium-doped fiber laser can be optimized.2.A self-made biconical fiber structure was used as a filter to add an erbium-doped fiber laser system.The immersion ratio of the 1978.8 nm band was 23dB,and the 3 dB bandwidth reached about 0.23 nm.Within 1 hour,the peak power fluctuation range was 2.2 dB;lasing laser in the 1997.8nm band and 1998.6 nm band,the 3 dB linewidth is 0.24 nm and 0.19nm respectively,the signal-to-noise ratio is30dB and 19dB respectively,and the peak power variation fluctuates below 3.85 dB;respectively at 1978.8nm,1990.8nm,1991.8nm band lasing laser.Among them,the power at 1978.8nm is higher,which can reach-40dBm,while the power at 1990.8 nm and 1991.8nm is-47 dBm,-44 dBm,and the signal-to-noise ratio is 27 dB,20 dB,22dB,respectively,and the 3 dB line width is at least At 0.2 nm,the peak power variation range is 4.2 dB,4.7 dB,and 5.3 dB,respectively.