Research On The Key Technologies Of High Power Thulium-doped Fiber Amplifier And Fiber Oscillator Laser

Due to its unique wavelength advantages,high-power continuous thulium-doped fiber lasers can be widely used in biomedicine,laser detection and sensing,laser industrial processing,defense and military fields,and are also excellent pump sources for generating 3-5 μm lasers.With the needs of the market,the power and performance requirements for 2μm lasers are also getting higher and higher.This paper is based on the status quo of high-power thulium-doped fiber lasers,and explores the key technology of high-power thulium-doped fiber lasers.Researched on this:(1)Theoretical analysis of thulium-doped fiber laser amplifier.The theoretical model of the thulium-doped fiber amplifier is established,and the theoretical calculation of the model is carried out.From the simulation results,it can be concluded that the output power of the backward pump is the highest,and the output power of the forward pump is the lowest.According to the simulation results,combined with the existing equipment in the laboratory,the pump source is 50 W,and the fiber length is 2m.At this time,the simulation can obtain 6.5W Theoretical output results.The thermal effect of the fiber laser is analyzed to obtain the distribution of the fiber in the axial and radial directions when the pump source is 50 W and 30 W and the fiber length is 3m.(2)Preliminary experimental construction and result analysis of the thulium-doped fiber laser amplifier.The measured output wavelength of the thulium-doped fiber laser amplifier is 2007 nm,the line width is 0.26 nm,the output power is 4.78 W when the input is 40 W,and the slope efficiency is 12.5 %.The degree of polarization of the thulium-doped fiber laser amplifier was measured,and the result was 17.9d B.The power stability of the amplifier is measured for half an hour,and the stability of the amplifier is 1%,and the return light is within the tolerance range.(3)Theoretical research and scheme design of the thulium-doped fiber laser amplifier for continuous amplification,and the problems that need to be considered when continuing to amplify,such as the mode field adaptation problem,the fiber end face problem,and the processing problem of large core diameter fibers.A two-stage bidirectional pump amplification scheme is designed,and the output power characteristics of each stage in the MOPA amplification scheme are calculated.The calculation results show that the second-stage amplification power can reach 651.52 W,and the third-stage amplification power can reach 1292 W,which is in line with the expected target.(4)The high-power thulium-doped fiber oscillator was experimentally constructed and the results were analyzed to measure the output power at different temperatures.It was found that in a certain water-cooling temperature range,with the decrease of the temperature,the output power and slope efficiency increased.And the optimal temperature is 14 o C,the pump power is 38.2W,the output power is 4.8W,and the slope efficiency is 17.7%.The oscillator spectrum was measured,and it was found that the wavelength moved to the long wavelength direction with the increase of temperature,and the stability was measured,and the stability was 1.5%,and the output power of the pump continued to increase.