Interaction Analysis Between Laser And Optical Material

As the substrate of laser coatings,the laser damage characteristics of K9 glass can directly influence on the performances of laser coatings such as AR and polarizer.Based on the stress relaxation model in 1D planar geometry and the visco-elastic constitutive equation, the temperature and stress histories in the K9 glass samples irradiated by CW laser beams (λ=1.06μm) have been calculated.The results indicate that the residual tensile stress due to the stress relaxation effect during cooling after the laser radiation may be greater than the tensile fracture strength of samples,while the maximum compression stress during the laser heating is less than the requirement for compression damage.For a K9 glass window of 3mm thickness,its damage due to the stress relaxation may be induced by a laser radiation of 0.946MW/cm~2 for 0.2s.Therefore,the stress relaxation should be regarded as the main mechanism of damage in K9 glass windows while a CW laser beam(λ=1.06μm) irradiates it with large spot.