Experimental Research And Engineering Design Of Passively Q-Switched Laser Based On Composite Crystal

Passively Q-switched solid-state laser is widely used in laser ranging,laser processing and nonlinear frequency conversion due to its advantages of narrow pulse width(nanosecond or sub-nanosecond),high peak power(tens or even hundreds of kilowatts),high beam quality,small size and simple structure.Aiming at the problems of low conversion efficiency and obvious thermal effect in ordinary composite crystals,a new composite crystal Yb:YAG/YAG/Cr:YAG/YAG is innovatively proposed in this paper,and through experimental comparison,it is verified that the four layer composite crystal has better output parameters.The specific research contents of this paper are as follows:1.Taking Yb:YAG and Cr:YAG crystals as examples,the establishment process of passively Q-switched pulse is analyzed by coupling rate equation,the relationship between Q-switched pulse output parameters and pump power,output mirror transmittance,Cr: YAG initial transmittance is studied,and the reasons for the change trend are analyzed from the micro level.2.Yb:YAG/YAG/Cr:YAG/YAG composite crystal and Yb:YAG/Cr:YAG/YAG composite crystal are compared experimentally,the passively Q-switched laser based on Yb:YAG/YAG/Cr:YAG/YAG composite crystal has better laser output performance.Meanwhile,the influences of the transmittance of coupling output mirror and pump spot on the output parameters of passively Q-switched pulse are studied.As can be known from the experimental results,compared with Yb:YAG/Cr:YAG/YAG laser,the maximum average output power,pulse energy and pulse peak power of Yb:YAG/YAG/Cr:YAG/YAG composite crystal are increased by 5.6%,14.7% and22.2%,respectively,the beam quality has also been improved.When the pump power is 17 W,the optimized Yb:YAG/YAG/Cr:YAG/YAG finally achieves the maximum average output power of 7.41 W,repetition frequency of 25.5 k Hz,pulse width of 4.6ns,pulse energy of 290.6 μJ,peak power of 63.2 k W,slope efficiency of 57.0%,optical efficiency of 43.6%,respectively.3.The Yb:YAG/YAG/Cr:YAG/YAG passively Q-switched laser system is designed by optical-electro-mechanical integration.The optical cavity,circuit control and heat dissipation are integrated into a 200×150×140 mm box.The optimal process and detail design of each part are given,and the performance of the prototype is tested.The test results show that the prototype has excellent output performances and can operate stably for a long time.