激光辐照下金纳米缺陷诱导光学玻璃损伤特性

采用离子束溅射的方式,在K9玻璃基片表面引入金纳米杂质缺陷,通过原子力显微镜(AFM)测得金纳米尺寸直径在50~100 nm之间。采用不同能量密度的激光对样品进行点阵式的单脉冲辐照(1-on-1)并且对损伤阈值及典型损伤形貌进行了实验及理论分析。损伤阈值采用零几率处的损伤密度。结果表明:引入金纳米杂质缺陷后其抗激光损伤阈值由裸基片的26.6 J/cm2下降为15.5 J/cm2。通过微分干涉显微镜,随着激光能量的增加,损伤呈爆炸坑形貌,主要呈现纵向加剧损伤。金纳米杂质缺陷在K9玻璃基片上形成了强吸收中心(引入金纳米杂质K9玻璃基片的弱吸收(47.33 ppm,1 ppm=10-6)是裸K9玻璃基片(3.57 ppm)的13倍)造成局部高温,这是造成损伤的诱因。通过计算,金纳米杂质对K9玻璃基片的作用包括两部分:当激光辐照在K9玻璃基片上,首先是热应力引起玻璃的破裂;随后杂质汽化产生的蒸汽压加剧材料的破坏,引起局部炸裂。

Damage mechanisms of optical glass with gold nano-defects under laser irradiation

Gold nano-defects(diameter=50-100 nm, AFM) were embedded in K9 optical glass by ion beam sputtering. The Laser-Induced Damage Threshold (LIDT) under 1-on-1 laser irradiation of the glass were investigated according to ISO 11254-1, respectively. The LIDT was defined as the incident pulse's energy density when the damage probability started to increase from zero (in joules per square centimeter), and it could be obtained by linear extrapolation of the damage probability data to zero damage probability. By analyzing the LIDTs, the LIDTs with optical glass embedded gold nano-defects were decreased from 26.6 J/cm2 to 15.5 J/cm2. Typical damage micrographs of optical glass embedded gold nano-defects were obtained by Nomarski microscope, showing vertical damage morphologies(explosion craters). Through the results of weak absorption(the weak absorption of optical glass embedded gold nano-defects was 47.33 ppm, 13 times to that of bare K9 optical glass), gold nano-defects formed strong absorption centers and caused local high temperature. Through theoretical calculation and simulation,damage mechanisms of optical glass with gold nano-defects under laser irradiation consisted two parts: (1) while in the optical glass embedded gold nano-defects, before the nano-defects boils, thermal stress exceeds the materials' mechanical strength, leading to mechanical damage. (2) If the nano-defects are vaporized, steam pressure intensified the destruction of the material and caused local crack.