Research On 3?m Gain Modulation And Mode-locked Laser Based On Fluoride Fiber

Compared with the traditional solid and gas lasers,fiber lasers have the advantages of good beam quality,small size,high conversion efficiency and good heat dissipation.In the near infrared band,fiber lasers and fiber Raman lasers have been widely used in communication,industry,medical and national defense,etc.However,there are still many problems and gaps to be explored in the development of short-pulse fiber lasers in the 3?m band.In this paper,a rare earth doped ion fluoride pulsed fiber laser has been realized by means of 3?m band mode-locking and gain modulation.Firstly,the application of 3?m fiber lasers is introduced,and the luminescence mechanism of 3?m doped Ho³⁺,Er³⁺and Dy³⁺ZBLAN fiber lasers is described.The research status of continuous and pulsed fiber lasers is introduced.The significance of this research direction is put forward according to the present situation.Then,the passive mode-locked fiber laser is simulated by MATLAB,and the principle of passive mode-locked fiber laser equation is analyzed.The second order distributed Fourier method is used to solve the Ginzburg-Landau equation,and the output characteristics of passive mode-locked fiber lasers based on saturable absorbers are explored.Combined with the numerical simulation results,the experiment of passive mode-locked fiber laser based on saturable absorber is carried out.The characteristics of a new two-dimensional material titanium carbide were introduced,and the titanium carbide thin film attached to the gilded mirror was prepared.The Ho³⁺/Pr³⁺co-doped ZBLAN passive mode-locked fiber laser was successfully realized by using this material.The pulse repetition frequency was 27.1MHz,and the average output power was up to 50m W.Then,by analyzing the theoretical model of Dy³⁺ZBLAN gain modulation,the rate equation of the Dy³⁺two-level structure in the 3?m band is constructed.At the same time,the finite difference time domain method is used to carry out the numerical simulation by MATLAB.The factors that affect the performance of Dy³⁺ZBLAN gain modulated fiber laser are analyzed,and the relevant results that the pump pulse width has the greatest influence on the gain modulation output are obtained by exploring the gain modulated laser threshold,pump pulse width and fiber length respectively.Finally,a Dy³⁺gain modulated fiber laser system is constructed.The Dy³⁺ZBLAN gain modulated fiber laser is divided into two parts:2.8?m pulse pump source and Dy³⁺ZBLAN gain modulated fiber laser.Using Fe²⁺:Zn Se crystal,a 2.8?m Er³⁺ZBLAN passively Q-switched fiber laser is realized as a pulse pump source.The central wavelength of the output pulse is 2886.3nm,the repetition frequency can reach 80k Hz,and the average power can reach 0.9W.The experimental device of Dy³⁺ZBLAN gain modulation laser was designed and built,and the problems in the experimental process were analyzed to further optimize the experiment.