Study On 2 μm High Energy Pulsed Thulium Doped Fiber Laser

2 μm laser is in the safety band of human eyes,with strong water absorption and low atmospheric transmission loss.It is widely used in biomedical,material processing and environmental monitoring fields.In recent years,research on 2 μm thulium-doped fiber lasers has focused on the output power,tunable range of wavelength,single frequency output and pulse energy of thulium-doped fiber lasers.In the aspect of realizing 2 μm large energy pulse,the width of dissipated soliton resonance module-locked(DSR)pulse is wider,and its pulse energy improvement space is larger,which can reach hundreds of nm.However,at present,2 μm band DSR mode locking is mainly realized in the "σ" shape cavity or " 8/9 " shape cavity based on NOLM,but there is little research on the real saturable absorber.Semiconductor saturable absorption mirror(SESAM)can flexibly regulate its saturation parameters during the preparation process,which is of great significance for further research and optimization of DSR pulse.Therefore,this paper takes thulium doped fiber laser as the research object,theoretically establishes the DSR lock imitation true model,and realizes the DSR pulse output based on SESAM lock mode in the experiment.,the pulse energy is greatly improved,and the influence of the dispersion parameters on the output performance of the fiber laser is further studied by the dispersion management of the resonator.The main research work of this paper includes:1,Theoretically studied the DSR in the mode-locked fiber laser pulse principle and output characteristics,based on gold at landau equation for 2 μm mode-locked dissipative soliton resonance thulium doped fiber laser has established the theoretical model and numerical simulation,the simulation result shows the cavity laser inside the progressive realization of the DSR pulse,further proves the saturable absorber of saturated absorption effect is a key factor in forming the DSR pulse.2,Mode-locked pulses generated by ordinary fiber lasers are subject to high nonlinear effects,and are prone to pulse splitting at high gain.The pulse energy is relatively low,generally around 1nJ.We constructed a 2 μm doped thulium fiber laser based on SESAM mode-locked.By optimizing the experimental scheme,we achieved a large energy pulse output with the central wavelength of 2003 nm,pulse energy of 5.07 nJ,and corresponding output power of 55.8 mW,and further observed the soliton molecular phenomenon in the experiment.3,Anti-saturation absorption effect plays an important role in the generation of DSR pulse.Currently,most of 2 μm-band DSR mode-locked fiber lasers are realized based on NOLM mode-locked technology,and few reports have been reported on the real saturable absorber.In this paper,the DSR pulse output based on SESAM with a maximum energy of 61.27 nJ is realized under the conditions of large positive dispersion by utilizing the reverse saturation effect of two-photon absorption in SESAM and the dispersion management of thulium-doped pulse laser.Finally,it is concluded that the larger the net dispersion value in the cavity of DSR pulse fiber laser,the higher the pulse splitting threshold and the higher the pulse energy.