Contaminant Resistant Sol-Gel Coatings

Valerie Rapson Greece Olympia High School Advisor: Kenneth L. Marshall University of Rochester Laboratory for Laser Energetics Summer High School Research Program 2005 1. Abstract Sol-gel coatings are used on the OMEGA laser optics as anti-reflection (AR) coatings to maximize their transmittance. Over time, trace organic compounds in the laser bay contaminate these sol-gel coatings, reducing their efficiency as AR coatings. Consequently, the optics must be removed, cleaned and re-coated with the sol-gel AR approximately every three months. In April of 2005 Y. Xu et al 1 demonstrated that changing the chemical composition of the sol-gel would reduce its susceptibility to contamination. In the work reported here, dimethyldiethoxysilane (DDS) and methyltriethoxysilane (MTES) were used to modify standard sol-gel solutions based on tetraethylorthosilicate (TEOS) in order to increase its resistance to contamination by volatile and semi-volatile contaminants. The methyl groups in the added components reduce the number of active OH groups available for hydrogen bond formation with contaminants in the air. The resulting coatings show improved contamination resistance, can be applied to OMEGA optics with only minimal changes to the current spindeposition process, and show equivalent or superior laser damage resistance to current sol-gel AR coatings used on OMEGA.