论文部分内容阅读
激光核聚变研究用的高功率固体激光器的出现,要求大的光学元件严格保持清洁。即使是一个微小的灰尘颗粒或一层被污染的薄膜,在激光作用下,都可能引起代价昂贵的破坏。因此,控制和消除污染已经成为激光核聚变计划中一个不可缺少的部分。光学表面的污染在两个主要方面限制了高功率激光器的特性。在激光放大器中,高强度的闪光灯可以使光学表面上的污染物热到足以造成局部熔化和破坏的程度。污染物的存在也可以贴在激光束上造成强度调制,这种调制可能引起激光束的自聚焦,进而使随后的光学序列的元件局部加热,而且还能使局部的光束强度超过高质量光学薄膜的破坏阈值——所有这些效应,都使激光核聚变应用中所需的可聚焦功率减小。我们已经发展了一大批关于清洁度的标准、测量方法以及制作工艺,从而使我们能够明确定义一个清洁的表面,确定污染的程度和提供适当洁净度的光学表面。污染控制技术开始使得光学表面在镀膜前、在装配期间以及在整个使用寿命期间,都免受颗粒污染。在Shiva激光系统中,这种技术实际上已经消除了污染所引起的故障。
The emergence of high-power solid-state lasers for the study of laser fusion requires that large optical components be kept strictly clean. Even a tiny dust particle or a contaminated film can cause costly damage under the action of a laser. Therefore, controlling and eliminating pollution has become an indispensable part of the laser fusion program. Pollution of the optical surface limits the characteristics of high-power lasers in two major ways. In laser amplifiers, a high-intensity flash can heat contaminants on the optical surface to a degree sufficient to cause local melting and destruction. The presence of contaminants can also be applied to the laser beam to create an intensity modulation that can cause self-focusing of the laser beam, which in turn heats the elements of the subsequent optical sequence locally and also allows the local beam intensity to exceed that of a high quality optical film The damage threshold - all of these effects - all reduce the amount of focus power required in laser fusion applications. We have developed a large number of standards, measurement methods, and manufacturing processes for cleanliness that allow us to define a clean surface clearly, determine the degree of contamination and provide an optical surface with proper cleanliness. Pollution control technology has begun to keep optical surfaces from being contaminated with particles before they are coated, during assembly and throughout their useful life. In Shiva laser systems, this technique has virtually eliminated the problems caused by contamination.