Optical Diagnostic And Analysis Of Thermal Distortion On Thin-disk Laser Crystal

With the rapid development of the laser diode stack array, Yb:YAG laser medium withquasi-three-level structure has received more and more attention, and has become one of thehotspot in research of solid state laser. Thin-disk laser has achieved high peak power, highaverage power and high conversion efficiency of laser output because of the breakthrough interms of crystal structure geometry, type of cooling and multiple-pass pumping technology,then thin-disk laser becomes a typical representative of industrial and scientific research ofsolid state laser. At the same time, with the achievement of higher output laser power,thermal distortion of disk crystal and the optical path difference become one of the importantfactors of output power and beam quality, so the analysis about the thermal distortion of diskcrystal by optical diagnosis method provides favorable technical support to furtherdevelopment of thin-disk laser.In this thesis, the corresponding mathematical model of the optical path differencetheory analysis is established, which is based on heat generating mechanism and temperaturecharacteristic of Yb:YAG crystal with quasi three level structure. At the same time, thedistribution of the OPD is obtained, the optical path difference(OPD) is Aspheric distribution,which is caused by temperature distribution, thermal stress, strain and deformation ofhigh-reflection coating. On the other hand, the OPD distribution of disk crystal is acquiredby Twyman-Green interferometer, and using Zernike polynomial to have a comprehensivemeasurement diagnosis and analysis of thermal distortion on thin-disk crystal. Then divideOPD into spherical and aspherical part.to have a deep analysis. At the same time, thevibration factors (such as water impact vibration and air cooling heat disturbance) weremeasured and analyzed.