Study on Contamination Control of Optical Thin Films with First Contact TM

Abstract

In high power laser system, it is very lethal of contamination on the surface of optical thin films. The contamination can be heated and burn rapidly under high power laser irradiation, which would result in damage to the optical thin films or even the whole optical component. Therefore, it is the key to control the contamination on the surface of optical thin films. First ContactTM can be used to clean the surface of optical thin films, remove fingerprints, dust and other contamination attached to the surface of optical thin films. It has been applied in many important projects such as aLIGO. In this paper, the First ContactTM was used to clean the optical thin films for chemical lasers. A microscope was used to test the appearance of the optical thin films before and after cleaning, which showed that, the First ContactTM is able to remove contamination, such as fingerprints and dust, attached to the surface of optical thin films for chemical lasers. The absorption coefficients of the optical thin films before and after cleaning were measured by an intra-cavity device, which is 286.5ppm and 216.9ppm respectively. The absorption coefficient was decreased by 24.3% after cleaning. The above results show that, the First ContactTM can effectively clean the optical thin films for chemical lasers, and there is no First ContactTM remain on the surface of optical thin films. It is found that the shortcoming of the First ContactTM is that, it cannot repair the defects in the substrates or optical thin films of the optical components, and cannot clean the optical thin films online. Finally, the use of First ContactTM was optimized, and the optimized method is conducive to the long-term preservation of optical components.