Research Of Mechanical-properties Damage Effect On Fused Silica

In building the high power laser system, the load capacity is one of the mainproblems that must be considered, since it is the ultimate limitation for the outputcapacity of the laser system.Therefore, the research on the anti-laser damage capacity of optical element hasalways been the hot-spot in the field of high power laser system. In return, everyprogress in the anti-laser damage capacity will always result in the leap in the outputcapacity of the laser system.The fused silica has been comprehensively used in the high power laser system, forthis superiority in optical performance and anti-radiation capacity. Lots of people haveconducted a plenty of theoretical and experimental researches, but very few of themhave concerned the impact of the mechanical specifics on the anti-radiation capacity ofthe fused silicaIn fact, nowadays the main stream methods to increase the anti-radiation capacityof the fused silica have more or less to be connected with the change in the mechanicalspecifics, such as HF surface etching, which deactivate the micro-crack and avoid thestress concentration, therefore increase the anti-tension capacity of the fused silica; CO2laser maintainance, which is the thermal treatment to the initial damage point, changethe stress distribution around the damage point and hence raise the mechanicalperformance around it.This paper has dealt with the impact of the mechanical specifics (the surfacestrength and hardness of the fused silica) on the anti-radiation capacity of the fusedsilica. The surface strength can be varied by apply a uniform stress layer on the surfaceof the fused silica to raise the anti-tension capacity.Meanwhile, hardness is one of themechanical performances of the fused silica.Main body：1. The code simulation shows that when the boundary of the fused silica underexternal constraint, the stress in a certain point in the surface of the fused silicaincreases with the deformation of the center point. If the deformation of the center point remains constant, the stress in the circular ring also remains constant and it decreasesaccording to the distance from the center.2. The damage threshold and the damage growth threshold are measured underdifferent surface stress states by applying external forces to the fused silica. And it isfound the damage threshold can be raised by the proper uniform distributed stress, butthe damage growth threshold will be lowered under this condition. Excessive stress willlower the damage threshold for worsening the surface mechanical performance. Surfacetension is bad to increase the damage threshold.3. The fused silica of the same specifications from different manufacturers havebeen tested by pressing in method. The triple frequency laser damage experiments arecarried out under different hardness. The conclusions are: the damage threshold varieslinearly with the hardness in a certian range and it tends to be saturated when thehardness reach a certain value.