Characterization of absorption and scatter losses on optical components for ArF excimer lasers

The performance of DUV optical components is assessed by measuring both absorption and scatter losses during ArF excimer laser irradiation. Absolute absorptance is determined by employing a high-resolution calorimetric technique which provides greatly enhanced sensitivity compared to transmissive measurements. Thus, the determination of single and two-photon absorption coefficients at energy densities of several 10 mJ/cm2 is accomplished. As a result of its sensitivity, UV laser calorimetry can be also employed for fast monitoring of laser induced aging phenomena like color center formation in fused silica or CaF2. For monitoring of the scatter losses in UV optics, a total scattering setup was recently installed, using an ArF excimer laser as pulsed 193nm light source and a Coblentz hemisphere as integrating element. Results of quantitative absorption and scatter measurements at 193 and 248 nm are presented for coated and uncoated optics, and the contribution of the various loss channels is discussed.