Suppression Of Overshoot Effect In High Power Fiber Laser Based On Pump Modulation

High power fiber laser has been widely used in industry,national defense,medicine and other fields because of its good performance.However,with the increasing of the output power,the overshoot effect causes ultra-high laser power density and a large amount of deposited heat load in the fiber,which becomes one of the main factors to destroy the output characteristics of the fiber laser and limit the further improvement of the power.How to effectively suppress the overshoot effect has become one of the problems to be solved.The overshoot effect can be suppressed by optimizing the length of gain fiber,reflectivity of fiber grating,pump wavelength and pump mode,but the optimization of these parameters will cause changes in laser output power,beam quality and spectral characteristics.Therefore,this paper proposes a method to suppress the overshoot effect of high power fiber laser based on pump modulation.Aiming at the mechanism and suppression of overshoot effect,starting from the system structure and working principle of high power fiber laser,based on the rate equation and power transmission equation,the static and transient characteristics of fiber laser are simulated and analyzed;based on the dynamic equation of laser overshoot,the analytical solution of laser overshoot is obtained by using small signal approximation method,and the generation mechanism of overshoot effect is simulated and analyzed Biological mechanism and its influencing factors.Finally,combining with the theoretical model and simulation results of the overshoot effect of fiber laser,a method to suppress the overshoot effect of high power fiber laser based on pump modulation technology is proposed.Aiming at the pump modulation technology,based on the linear closed-loop negative feedback,an analog PID controller and a time-delay network are added to design a pump modulation circuit suitable for high-power fiber laser,and its modulation performance is verified by simulation.Design and build the pump source test platform,fiber fusion loss test platform and combiner efficiency test platform,carry out a series of experimental analysis on each optical device,on this basis,build a 750 W fiber laser oscillator system.At the same time,the laser power supply and control system suitable for 750 W fiber laser are designed,and the hardware design and implementation of each functional module in the system are carried out.On this basis,the laser power supply and control system whose parameters meet the expected requirements are built.In order to verify the suppression effect of pump modulation technology on the overshoot effect of high-power fiber laser,the laser power supply and control system are applied to 750 W fiber laser oscillator for experimental research.The experimental results show that: after pump modulation,the peak power of 1450 W fiber laser overshoot attenuation is 2.86 d B,and the delay time to achieve the rated laser power is less than 1 ms.