Patent ID: 7742156

Claim:
An optical material for making optical components for lithographic applications, wherein said optical material is selectable by a testing method, said testing method comprising the steps of: a) irradiating an optical material to be tested with ultraviolet radiation at a wavelength below 250 nm, determining intrinsic fluorescence intensity at 285 nm, determining non-intrinsic fluorescence intensity at a wavelength of 740 nm, and subsequently determining a ratio of the non-intrinsic fluorescence intensity to the intrinsic fluorescence intensity; b) irradiating the optical material to be tested with laser light and measuring a difference between respective absorptions at a wavelength of 385 nm before and after irradiation with the laser light; and c) irradiating the optical material to be tested with an energetic radiation source until saturation is achieved and measuring a change in absorption at 265 nm before and after irradiation with said energetic radiation source; wherein said energetic radiation source is an X-ray source or a radioactive source; and wherein said optical material is selectable for making said optical components if the ratio of the non-intrinsic fluorescence intensity at 285 nm to the intrinsic fluorescence intensity at 740 nm is less than 1:100, said difference between said respective absorptions at 385 nm before and after the irradiation with the laser light is less than 2.5×10 −3 cm −1 ; and the change in the absorption at 265 nm before and after irradiation with the energetic radiation source is less than 50×10 −3 cm −1 .