Study On The Operation Mode Of Solid-state Laser Based On Super Gaussian Pump Beam

All the time,all-solid-state lasers have been favored in the laser field.Among them,the 1.34 ?m laser light source plays an important role in optical fiber communications,laser medicine,quantum information,and air pollution monitoring.With the birth of lasers,the optimization of lasers working efficiency and beam quality has become the focus of research.There are many factors that affect the efficiency of lasers,such as the choice of pumping mode,cavity design,temperature control,and so on.This thesis studies the operation characteristics of solid-state lasers,from the aspects of pump source pumping model,energy level rate equation and thermal effect,etc.The main contents are as follows:1)Converting the pump light Gaussian distribution model into a super-Gaussian distribution model.In the derivation of the Nd:GdVO4 crystal four-level rate equation,the effect of the up-conversion process on the number of particles in the laser's upper energy level inversion is added,including energy transfer up-conversion(ETU)and excited-state absorption(ESA).From the optimized rate equation,it can be deduced that under the normal operating conditions of the laser crystal,the particle ratio of the four different energy level transition processes in the pumping process.Numerical calculated of the relationship between the particle ratio and pump power under the pump light super-Gaussian model.At the same time,the influence of factors such as the mode overlap rate and the pump light spot radius on the particle ratio of the four energy level transitions is also considered.Further calculations are made on the implicit function relationship between pump power and output power.The results show that the pump light model based on the super-Gaussian distribution can increase the output efficiency of the laser to a certain extent.2)The crystal heat source transfer model is established,the lens focal length and the expression of thermally induced diffraction loss are derived,and numerically calculate the relationship between the pump power and the thermal lens effect.By comparing the different heat source functions under the Gaussian distribution and the super-Gaussian distribution of the pump light,the influence of the pump power and mode overlap rate on the thermally induced diffraction loss is studied.Starting from the particle energy level transition mechanism,theoretically calculate the thermal deposition percentage of the laser gain medium.Finally,it is concluded that the use of a super-Gaussian pump light model can better optimize the thermal effect of the laser.3)Choose CCD as the experimental detector,design a test plan for the intensity distribution of the pump spot,measure the intensity distribution of the spot under different optical pump powers,and use the super-Gaussian function to fit the test data.The results show that when the optical pump power is less than 10 W,the pump light intensity distribution is more closely aligned with the Gaussian distribution.When the optical pump power is 10 W to 50 W,the pump light intensity distribution gradually conforms to the super-Gaussian distribution with super-Gaussian order m=2.Then,the equivalent thermal resistance is used instead of the laser medium,and the heating power is obtained by measuring the current at both ends of the thermoelectric cooler(TEC)to further measure the thermal deposition percentage of the laser.The experimental measurement results are basically consistent with the theoretical calculation results.Under the condition of ensuring the stability of the resonator,the flat-concave cavity structure is used to conduct experimental research on the output characteristics of the laser.Finally,it is concluded that the super-Gaussian distribution model of m=2 is more in line with the relationship of the laser output characteristics than the Gaussian distribution model.So as to verify the rationality of this thesis.