Gallais Laurent, Cormont Philippe, Rullier Jean-Luc
Institut Fresnel, CNRS, Aix-Marseille Université, Ecole Centrale Marseille, Campus de Saint-Jérôme, 13013 Marseille, France.
Opt Express. 2009 Dec 21;17(26):23488-501. doi: 10.1364/OE.17.023488.
Laser damage mitigation' is a process developed to prevent the growth of nanosecond laser-initiated damage sites under successive irradiation. It consists of re-fusing the damage area with a CO2 laser. In this paper we investigate the stress field created around mitigated sites which could have an influence on the efficiency of the process. A numerical model of CO2 laser interaction with fused silica is developed. It takes into account laser energy absorption, heat transfer, thermally induced stress and birefringence. Residual stress near mitigated sites in fused silica samples is characterized with specific photoelastic methods and theoretical data are compared to experiments. The stress distribution and quantitative values of stress levels are obtained for sites treated with the CO2 laser in various conditions of energy deposition (beam size, pulse duration, incident power). The results provided evidence that the presence of birefringence/residual stress around the mitigated sites has an effect on their laser damage resistance.
“激光损伤缓解”是一种为防止在连续辐照下纳秒激光引发的损伤部位扩大而开发的工艺。它包括用二氧化碳激光重新熔化损伤区域。在本文中，我们研究了缓解部位周围产生的应力场，该应力场可能会对该工艺的效率产生影响。建立了二氧化碳激光与熔融石英相互作用的数值模型。该模型考虑了激光能量吸收、热传递、热致应力和双折射。采用特定的光弹性方法对熔融石英样品中缓解部位附近的残余应力进行了表征，并将理论数据与实验数据进行了比较。获得了在不同能量沉积条件（光束尺寸、脉冲持续时间、入射功率）下用二氧化碳激光处理的部位的应力分布和应力水平定量值。结果表明，缓解部位周围的双折射/残余应力的存在对其抗激光损伤能力有影响。
