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多层介质膜光栅是高功率激光系统的关键光学元件.为了满足国内强激光系统的迫切需求,首先利用考夫曼型离子束刻蚀机开展了HfO2顶层多层介质膜脉宽压缩光栅的离子束刻蚀实验研究.采用纯Ar及Ar和CHF3混合气体作为工作气体进行离子束刻蚀实验,获得了优化的离子源工作参数.结果表明,与纯Ar离子束刻蚀相比,Ar和CHF3混合气体离子束刻蚀时的HfO2/光刻胶的选择比大.HfO2的离子束刻蚀过程中再沉积效应明显,导致刻蚀光栅占宽比变大.根据刻蚀速率分布制作的掩模遮挡板可以提高刻蚀速率均匀性,及时清洗离子源和更换灯丝,可保证刻蚀工艺的重复性.利用上述技术已成功研制出多块最大尺寸为80 mm×150 mm、线密度1480线/mm、平均衍射效率大于95%的HfO2顶层多层介质膜脉宽压缩光栅.实验结果与理论设计一致,为大口径多层介质膜脉宽压缩光栅的离子束刻蚀提供了有益参考.
Multi-layer dielectric grating is the key optical component of high power laser system.In order to meet the urgent need of strong laser system in our country, firstly, Kaufman-type ion beam etching machine was used to carry out the HfO2 multilayer dielectric film pulse compression grating ion Beam etching experimental study.Using pure Ar and mixed gases of Ar and CHF3 as the working gas for ion beam etching experiments, the optimized working parameters of the ion source were obtained.The results show that compared with pure Ar ion beam etching, Ar and CHF3 The selectivity of HfO2 / photoresist for mixed gas ion beam etching is large, and the redeposition effect of HfO2 during ion beam etching is obvious, which leads to the widening of the proportion of the etching gratings.The mask fabricated according to the etching rate distribution The shielding plate can improve the uniformity of the etching rate, clean the ion source in time and replace the filament, which can ensure the repeatability of the etching process. The above-mentioned technology has successfully developed several pieces with a maximum size of 80 mm × 150 mm, a linear density of 1480 lines / mm and the average diffraction efficiency is more than 95%. The experimental results are in accordance with the theoretical design, which provides benefits for the ion beam etching of large aperture multi-layer dielectric film pulse width compression grating Test.