High-Reflectance Coatings at 193nm

As an important component in 193nm laser system, high-reflectance (HR) coatings with excellent optical and mechanical properties are needed urgently. In this study, we designed and produced three different HR coatings at 193nm, Al 2 O 3 / AlF 3 coating, LaF 3 / AlF 3 coating and a double stack mirror with combination of Al 2 O 3 / AlF 3 and LaF 3 / AlF 3 . With 14 layer pairs, the reflectance of Al 2 O 3 / AlF 3 coating could reach 98% which could not get higher duo to the absorption of Al 2 O 3 . The reflectance of LaF 3 / AlF 3 coatings could achieve 98.13% with 15 layer pairs. When the layer pair increased to 16, the reflectance lessened ascribed to steep rise in scattering loss caused by micro-cracks occurred in the coatings. A mirror with combination of Al 2 O 3 / AlF 3 and LaF 3 / AlF 3 could obtain the reflectance of 98.78% as deposited. Even 4 months later the value could still reach 98.47% which was an excellent candidate for practical application.