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采用Nd:YAG单纵模调Q激光器,研究了溶胶-凝胶SiO_2薄膜表面颗粒污染对激光辐照损伤的影响.实验表明当膜面存在颗粒时,激光破坏阈值明显降低.尤其是前表面颗粒,最容易诱导损伤,损伤斑中央处基底的烧蚀很严重,且伴有环状变化.从损伤形貌来看,污染后的薄膜更容易出现场致损伤和基底破坏.为了深入研究这一现象,采用了电磁波时域有限差分(FDTD)法对减反射薄膜表面的颗粒污染进行了模拟研究.结果表明,前表面颗粒的调制强度要大得多.颗粒污染诱导的调制最强区位于基底一侧一个波长内,容易诱发损伤.在元件体内,光强呈衰减趋势,在3倍波长深度后逐渐趋于稳定.颗粒物诱导激光损伤问题的量化,可为亚表面缺陷的检测和控制提供依据.
The effects of particle contamination on the surface of sol-gel SiO_2 film irradiated by laser were studied by Nd: YAG single-longitudinal-mode Q-switched laser. The experimental results show that the laser damage threshold is obviously decreased when there is particle on the film surface, , Most likely to induce damage, ablation of the base of the lesion at the center of the lesion is very serious, and accompanied by annular changes from the damage morphology, the contaminated film is more prone to field damage and damage to the substrate.In order to further study this Phenomenon of particles on the surface of antireflection thin film was simulated by finite difference time-domain (FDTD) method of electromagnetic wave.The results show that the modulation intensity of particle on the front surface is much larger than that of particle on the substrate Within one wavelength of one side, it is easy to induce damage.In the body of the device, the light intensity shows a declining tendency and tends to be stable after reaching the depth of 3 times the wavelength.The quantification of particle damage induced by laser can provide the basis for the detection and control of subsurface defects .