Research Of The Influence And Compensation Of The Misalignment Instability Of Thin-disk Laser Caused By Air Thermal Effect

Thin-disk laser plays an important role in the high power field.Although it effectively reduces the thermal-lens effect of the crystal,the thermal-lens effect still affects the output laser mode and stability.On the other hand,with the increase of the injection power,the thermal effect of the heated air in front of the thin-disk crystal,which is a significant factor in laser stability degradation and beam quality degradation of high-power,high-beam quality thin-disk laser,will have more and more serious effects on the stability and the beam quality of the laser.Therefore,the research on the misalignment stability of the system under the air-thermal effect is of great value and guiding significance for the reduction of misalignment of the thin-disk laser under high power.Firstly,the cause of the air-thermal effect is analyzed theoretically in this paper,and a three-dimensional model of air is established.After using the relevant theories of fluid mechanics and thermals to simulate in the Comsol software,the three-dimensional temperature distribution of air is obtained,which can be converted the temperature distribution into refractive index distribution and optical path.And Zernike polynomial is used to analyze the optical properties of hot air.The results show that there are two kinds of effects of air-thermal effect: one is equivalent to a concave lens,which is called air-lens effect,and the other is that the incident light is mainly deflected in the vertical direction,which is called air-wedge effect.Moreover,by increasing the flow rate of the vertical air or changing the air to a gas with a faster heat transfer rate such as helium,the air thermal effect can be reduced.This provides theoretical support for reducing air-thermal effect and has important guiding significance in experiments.Secondly,the offset instability of the thin-disk laser under the influence of air thermal effect is theoretically analyzed in this paper,basing on the light transmission matrix theory.And parameter G,which is related to cavity structure and pump,is defined to reflect the stability of the thin-disk laser.For G ?1,the laser is unstable the laser system is stable for G(27)1.It is further proposed that for the cavity satisfying G(28)0,reduces the misalignment of the system caused by air thermal effect.On this basis,the cavity structure is designed.Finally,the experiment to measure and analyze the power of the air-lens effect and the angular imbalance of the vertical direction caused by the air-wedge effect is designed,which verify the conclusions about the air-thermal effect.The resonant cavity structure satisfying G(28)0 is designed to effectively suppress the influence of air thermal effect on the stability of the output laser on the experimental platform.