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用离子束溅射的方法在红外石英玻璃基底上制备了Ta2O5/SiO2(1.064μm波长下高透,2.128μm波长下高反)波长分离膜,利用飞秒激光系统(输出波长为2μm,脉宽为80 fs)测试了它的激光损伤情况,同时用光学显微镜和扫描电镜观察了样品的损伤形貌,根据不同能量作用下破斑面积与能量密度的关系拟合得到样品的损伤阈值。实验结果表明,2μm飞秒激光作用在波长分离膜的损伤形貌为层状分布,破斑边缘比较清晰,没有热扩散和热传导现象,属于本征损伤。利用基于导带电子数密度的理论模型,并结合电场分布与带隙理论讨论了2μm飞秒激光作用于光学薄膜的损伤机制,确定了损伤起源于高低折射率界面处的窄带隙材料。
Ta2O5 / SiO2 (high permeability at 1.064μm wavelength and high anti-wavelength at 2.128μm wavelength) was prepared on an infrared quartz glass substrate by ion beam sputtering. By using femtosecond laser system (output wavelength of 2μm, pulse width 80s). The damage morphology of the sample was observed by optical microscope and scanning electron microscope. The damage threshold of the sample was obtained by fitting the relationship between the area of the broken spot and energy density under different energy. The experimental results show that the damage morphology of the 2 μm femtosecond laser beam is a layered distribution, the edge of the spot is relatively clear, there is no thermal diffusion and heat conduction phenomenon, which is an intrinsic damage. The damage mechanism of 2 μm femtosecond laser on the optical thin film was discussed by using the theoretical model based on conduction number electron density and the electric field distribution and band gap theory. The narrow band gap materials with damage originating at the interface of high and low refractive index were identified.