U. B. Schallenberg, H. Uhlig and N. Kaiser, Fraunhofer-Institution for Applied Optics and Precision Engineering, IOF Jena, Optical Coatings Department,
“Graded reflectance mirror design with unconventional profile for excimer laser,” Pure Appl. Opt. 3, 427-434 (1994)

Abstract:
The design of a graded reflectance mirror (GRM) for KrF excimer laser has been developed. The mirror consists of three areas of reflectance: (1) a rectangular area in the middle of the substrate with reflectance R₁ ~ 10%, (2) an outer area with reflectance R₂ ~ 95% and (3) a transition area between with an exactly defined increase in reflectance from R₁ to R₂. The GRM sandwich type was used for the mirror design with two layers of variable thickness and a total of 19 layers. The variable thickness is based on the shadowing effect of a fixed non-contact mask with rectangular aperture. For excimer laser applications in particular, the electric field distribution inside the layer system was investigated.