The Research Of Theory And Experiment Of 2.8?m Mid-infrared All-fiber Laser

Mid-infrared(Mid-IR)fiber laser covering the wavelength of 2.8?m has many crucial applications,such as military confrontation,medicine,remote sensing,spectroscopy and so on.It has been a research hotspot in the field of laser technology for many years to achieve high-power 2.8?m continuous wave(CW)output,high average and peak power pulse output,and integrated all-fiber laser structure.However,due to the incomplete technology of all-fiber optical device on Mid-IR zirconium fluoride based Er³⁺-doped fiber(Er:ZBLAN),the laser system has to rely on a large number of space-based optical devices,which seriously restricts the stability and output performance of the system.On the other hand,at the wavelength of Mid-IR in the Er³⁺-doped system,there is a serious quantum defect in the conversion of near-infrared pumping photons to signal photons,which always result in strong heat accumulation in the fiber core.Therefore,in order to obtain high power2.8?m CW and ultrashort pulse,it's important to make the theorical and experimental research for Er:ZBLAN laser system,optimize fiber parameters,design the cavity structure,and develop critical technology of all-fiber device.In this paper,we will focus on the research of Mid-IR Er:ZBLAN fiber laser system with space-based and all-fiber structure,including the research of CW and passive mode-locked system.In the first part,the research background and significance of the subject were described,and the research progress of mid-infrared Er:ZBLAN laser at home and abroad in recent five years was investigated,which included the theorical and experimental research of CW and pulsed laser.Then,the development of mid-infrared Er:ZBLAN fiber lasers and the existing problems to be solved were summarized,and the research target of this paper was defined.In the second part,the energy structure and the processes of energy transition in Er³⁺-doped ZrF₄-glass was analyzed,based on the common theory of rate-equations.And a simulated result about several parameters of fiber laser was presented.on the other hand,the mechanism of passive mode-locking technology was analyzed used the theory of wave optics and the Ginzburg-Landau equation in nonlinear optics respectively.In the third part,based on the numerical model of 3.5?m-DWP-Er:ZBLAN,an novel boundary value problem(BVP)algorithm was presented,which optimized the convergence speed,convergence accuracy and guessed value stability of the standard relaxation method(RM).The simulation and experimental results of the literature were restored,and the accuracy of the model and parameters can be effectively verified.Compared with the standard relaxation method,the performance of the new algorithm was proved to be more efficient.In the fourth part,an Er:ZBLAN free-run oscillator and soliton pulse amplifier at 2.8?m,based on space structure were built.The 2.8?m free-run oscillator can achieve the CW output with the power of 418.6m W,the centre wavelength from 2786to 2798nm and the spectral width of 7nm.The amplifier used the 2.8?m source of Raman soliton pulse as the seed source,which can amplify the average power from144m W to 1.031W without obvious self-excited oscillation.The output pulse has the spectral width of 26nm,and the slope-efficiency of 22.15%.The output power characteristic curves of the oscillator and amplifier were in good agreement with the theoretical simulation results.Then,a quasi all-fiber 2.8?m-Er:ZBLAN mode-locked oscillator and pulse amplifier were built based on the technology of fluoride fiber side-pumped coupler.The mode-locked pulse seed with the repetition rate of20.5948MHz and the average power of 27.6m W was realized.The seed was butt-coupled with the amplifier,and the average power of the mode-locked pulse was amplified to watt-level,which laid a foundation for the further pulse amplification,and the research of Mid-IR supercontinuum source and soliton self-frequency shift(SSFS).