Patent ID: 7961383

Claim:
An element for use in wavelengths less than 200 nm laser systems, said element comprising: a substrate, a plurality of periods of fluoride coating materials, each of said periods comprising at least one layer of a high refractive index fluoride material and at least one layer of a low refractive fluoride material, a plurality of layers of an amorphous SiO 2 based material selected from the group consisting of amorphous silica, amorphous F-doped SiO 2 , amorphous N-doped SiO 2 and amorphous Al 2 O 3 -doped SiO 2 , wherein one of said layers of amorphous SiO 2 is inserted between periods of said fluoride coating materials or between a stack of a plurality said periods, wherein said high refractive index fluoride material has an index in the range of 1.65 to 1.75 and said low refractive fluoride material has an index in the range of 1.35 to 1.45, and wherein the thickness of the amorphous SiO 2 layer inserted between the periods of high and low refractive index materials is in the range of 5 nm to 75 nm.