真空紫外Al/MgF_2反射镜

采用三步热舟蒸发制作法研制了真空紫外Al/MgF2反射镜,研究了改善制备工艺有效提升反射率的方法。在两层Al/MgF2反射镜制备过程中,第一步在室温石英基板上快速蒸发厚约70nm的铝膜;第二步在铝膜表面迅速蒸发厚约10nm的MgF2;第三步先对基板加热到一定温度后,再在Al+MgF2的表面上蒸发15~20nm厚的MgF2。通过调整基板温度(室温、100℃、200℃和300℃),研究了基板温度对Al/MgF2反射率的影响。真空紫外反射率计测试结果表明:第二步蒸镀MgF2之后增加基板温度有利于提高反射镜的反射率;MgF2薄膜的厚度对反射镜的反射率起到一定的调制作用,MgF2厚为26.7nm的反射镜在122nm处的反射率达85%。在实验室环境下存放1个月和5个月后,反射镜的反射率没有变化。研究结果为真空紫外光学系统需求的高性能光学元件的研制提供了技术基础。

Al/MgF2 mirrors in vacuum ultraviolet region

Al/MgF₂ mirrors in vacuum ultraviolet region were developed by three step thermal boat evaporation method, and a method to improve the reflectivity of mirrors by fabrication technology was explored. There are three steps to fabricate the two layers Al/MgF₂ mirrors. In the first step, an aluminum coating with a thickness about 70 nm was evaporated on a quartz substrate at the room temperature. And then, the MgF₂ coating with a thickness about 10 nm was quickly evaporated on an aluminum coating. In the third step, the substrate was heated to certain temperature, and the MgF₂ coating with a thickness of 15-20 nm was evaporated on the surface of the Al and MgF₂ coatings. According to changes of the substrate temperatures at the room temperature, 100, 200 and 300 ℃, the effects of the substrate temperatures on the mirror reflectivity were researched. The results measured by a vacuum ultraviolet reflector show that improving the substrate temperature after evaporating MgF₂ is in favour of increasing the reflectivity of Al/MgF₂ mirror and the thickness of the Al/MgF₂ is related to the reflectivity of the mirror. When the thickness of MgF₂ is 26.7 nm, the reflectivity at 122 nm is about 85%. The reflectivity of the mirrors stored in the laboratory is barely changed after one month and five months. The results provide technological function for higher performance optical elements in vacuum ultraviolet optical systems.