Scattering losses in fused silica and CaF2 for DUV applications.

Scattering losses for fused silica were measured over a wide wavelength range (193-800 nm) using different laser sources. The data indicate that scattering centers are smaller than similar to12 nm, and scattering is consistent with Rayleigh type even at 193 nm. Scattering losses scale with wavelength as 1/lambda(4), and scattering loss at 193 nm was found to be (0.65 +/- 0.08)x 10(-3)/cm absorption units or (0.15 +/- 0.02)% transmission per cm. CaF2 measurements were completed in the visible wavelength range. The experimental approach for DUV wavelength measurements for CaF2 is described. Estimated scattering losses at 193 nm are similar to0.003% transmission per cm and similar to0.006% transmission per cm at 157 nm. Data for CaF2 indicate deviation from Rayleigh-type scatter.