Research On Laser-Induced Stress Wave Behavior In The Damage Process Of Optical Components

UV laser-induced damage in optical components is the bottleneck of improving the load capacity of high-power solid-state laser device,especially in inertial confinement fusion(ICF)engineering.The mechanism of UV laser damage of optical elements is extremely complex and involves many physical processes,which has become the key point of ICF engineering research to break through.At present,the research on UV laser-induced damage of optical components focuses on the determination of damage threshold of optical components under different processing technology,the characterization and detection of initial micro-defects on the surface of the elements,the micro-morphology of the damage core area and the analysis of material morphology changes during the damage process.However,there is no complete and clear explanation of the mechanical wave behavior that ultimately cause materials to break and peel,and forms the stress distribution and propagation within a range far larger than the damage nuclear scale,including the types,distribution,strength and propagation rules of these mechanical waves in the damage process.In this paper,based on the basic principle of pump-probe method,an optical system of nanosecond time-resolved imaging for dynamic measurement of stress wave using orthogonal polarized photoelasticity method is designed and built,which is used to obtain the dynamic behavior image of rear surface damage stress wave of fused silica and KDP crystal.Furthermore,the magnitude scale of laser-induced damage stress intensity of fused silica material in the laboratory is obtained by means of photomechanics,and the stress wave distribution structure and attenuation evolution behavior are obtained.The results show that the damage of the large light spot size is mainly caused by the mechanism of defect induction;The damage stress wave of KDP crystal induced by ultraviolet laser includes fast wave and slow wave,and the damage stress wave of fused silica includes compression wave,shear wave and surface wave;The interaction between the two materials and laser increases under the cumulative irradiation of UV laser pump,only changes the stress wave intensity,and the propagation speed of the stress wave is maintained;In the early stage of the damage of fused silica,there are always strong surface waves and weak compression waves;The damage stress wave intensity of fused silica is of GPA magnitude,in which the stress intensity of surface waves is always greater than thatof compression waves and shear waves,and the attenuation speed of surface waves is the slowest,and the surface waves play a dominant role in the mechanical factors causing the damage;According to the picture of rear surface damage,the relationship between the damage stress wave behavior and the damage morphology is inferred.The experimental results obtained in this paper have certain reference value and significance for revealing the dynamic behavior characteristics of stress wave type,intensity,distribution evolution and so on in the process of laser-induced damage,and further clarifying the mechanism of damage kinetics.