Optimal Design Of High Gain Grazing Incidence Slab Laser Amplifier

With the rapid development of laser diode pumped technology,the emergence of new solid laser materials,and effective management of the thermal effect,the output power and beam quality of diode pumped solid state laser(Diode,Pumped Solid-state Laser,DPSSL)have been significantly improved,which has been widely applied to industrial production,medical,information technology,military,etc.In order to obtain high power and high beam quality laser,the main oscillator power amplification(MOPA)technology is usually used to amplify the laser power of the seed laser with low power and high beam quality.In recent years,side pumped slab laser amplifier with the Nd:YVO4 bounce configuration.strip structure has attracted wide attention of researchers.This type of laser amplifier makes the amplification more efficiently.At the same time,the good heat dissipation ability also makes the beam quality of the amplified laser guaranteed.However,the side pumped Nd:YVO4 bounce configuration is different from the traditional end pumped rod configuration in the pump condition,the thermal effect,the seed laser parameter,etc.,which needs further study.In this paper,a side pumped grazing incident Nd:YVO4 slab laser amplifier is analyzed to obtain a high gain and high beam quality laser amplifier.First,the thermal effect of the slab is further studied.The theoretical model of the temperature distribution for the Nd:YVO4 slab is established.The slab temperature distribution under different pumping conditions is analyzed.The result is that the variation of vertical pump diameter has little influences on the temperature distribution of slab.Therefore,the vertical pump diameter on slab amplifier can be as small as possible in order to obtain a higher pump power density.Secondly,based on the temperature distribution of Nd:YVO4 slab,the thermal distortion and thermal lens effect of slab amplifier are analyzed.The optimization design of the seed laser parameters of the grazing incident Nd:YVO4 slab laser amplifier is also carried out.By calculating the thermal distortion of different horizontal matching modes and different grazing incidence angles,it is found that for a certain pump power and horizontal mode matching ratio,a smaller grazing incidence angle can lead to lower horizontal thermal distortion.When the mode matching ratio between seed laser and pump laser in horizontal direction is 0.6,and the grazing incidence angle of seed laser is between 3 and 5 degrees,the extraction efficiency of seed laser is higher,and the horizontal thermal distortion is smaller.Finally,the single pass and multi-pass amplification experiments of the grazing incident Nd:YVO4 slab laser amplifier are carried out,and the rationality of the optimization design is verified.For single pass grazing incidence slab amplification,when the grazing angle is between 3 degrees and 4 degrees,the efficiency of seed laser extraction is the highest and the horizontal thermal distortion is relatively small.Thus,the amplified laser with high beam quality can be obtained.For the triple pass grazing incidence slab amplification,with the simulation analysis and experimental research,the optimal model matching ratio of in the horizontal direction is 0.6,and the grazing incidence angle is 3,5,7 degrees,respectively.The average power of seed laser is 2 mW and the beam quality M2=1.17.After the triple pass amplification,an output power of 12.6 W is obtained,corresponding to the peak power of 1.4 MW and pulse energy of 126 ?J.The optical-optical extraction efficiency is 28%and the beam quality factor M2=1.4.