摘要:
The method determines the extent of irreversible radiation damage of an optical material. The method includes the following three tests to determine the extent of irreversible radiation damage: 1) the optical material is irradiated with ultraviolet radiation at a wavelength of 193 nm and the non-intrinsic fluorescence intensity at a wavelength of 740 nm is measured; 2) the optical material is irradiated with high energy laser light and a change in respective absorptions at a wavelength of 385 nm is determined before and after irradiation; and 3) the optical material is irradiated with an energetic radiation source to form all possible color centers and a difference of respective surface integrals of corresponding absorption spectra in ultraviolet spectral and/or visible spectral regions is measured before and after irradiation.
摘要:
The method provides CaF2 single crystals with low scattering, small refractive index differences and few small angle grain boundaries, which can be tempered at elevated temperatures. In the method a CaF2 starting material is heat-treated for at least five hours at temperatures between 1000° C. and 1250° C. and then vaporized at a temperature of at least 1100° C. in a vacuum of at most 5*10−4 mbar to form a vapor. The vapor is condensed at a temperature between 500° C. to 1280° C. to form a condensate. Then a melt formed from the condensate is cooled in a controlled manner to obtain the single crystal, which is subsequently tempered. The method is preferably performed with a CaF2 starting material including waste material and cuttings from previously used melts.