Study On The Effect Of Spherical Aberration Of LD Pumped Laser Lens On The Quality Of Laser Beam

Improving the beam quality of the laser output beam is an important issue in the research of the solid state lasers.Based on the thermal lens effect of Nd:YVO₄ crystal,the spherical aberration is added to compensate for the spherical aberration in the main oscillator power amplifying structure,and the beam quality is optimized in a simple and reliable way.The research mainly includes the following:From the static heat conduction equation,combined with the finite element analysis software COMSOL to simulate the temperature distribution of the crystal through the crystal boundary heat accords with the experimental conditions the conversion conditions.And then get the working state of the crystal distribution of optical path difference calculated by the formula,the generalized inverse matrix of Zernike optical path difference polynomial calculation,obtained the distribution of crystal thermal lens aberration.The model is also treated with thin slice,which proves that the spherical aberration is accumulative.From the perspective of the beam quality factor M²,the primary difference with Seidel theory,sorting out the relationship between the spherical aberration and the beam quality factor M²,and simulate the beam quality factor M² with spherical aberration changes;at the same time using the Hartmann wavefront sensor in the experiment of laser wave forward measurement,obtained the Zernike polynomial distribution of wavefront phase distortion,which can be found in spherical aberration distortion.The aberration of spherical aberration under experimental conditions is obtained,and the measured results are good agreement with the simulation results.The beam quality and phase distribution of the resonator are measured experimentally.Based on the previous experimental results and analysis,a single-state and single-pass amplifier is built to compensate the beam quality deterioration in the process of power amplification.By imaging the phase of a specific position to the amplifying crystal,by adjusting the pump power of the amplifying stage and changing the spherical aberration of the amplification stage,the spherical aberration of the two crystals of the local oscillator and the amplification stage is accumulated and compensated,which improves the beam quality of the output beam.When the resonators'output power is 9.2W,and amplifiers'pump power is zero,the output beam quality of the total isM_x²=.210,M_y²=.203,the spherical aberration coefficient-0.29?;When the increase of the pump power of amplifier,output power is 10.54W,the beam quality is optimized?M_x²=.154,M_y²=.139?.the spherical aberration coefficient is-0.02??almost zero?;With the continuous increase of pump power of amplifier,the total output power is 11.3W,the beam quality is compensated and the beam quality is deteriorated,and the spherical aberration coefficient is 0.39?.In addition,a controlled experiment is built to verify the reliability of this method.