Browsing by Author "Apel, O."

A sensitive total-scattering measurement setup for the DW spectral range is presented, which allows precise determination of both forward and backward scatter losses from optical components for excimer lasers with a sensitivity below 10 ppm for 248 nm and 50 ppm for 193 nm. Scattering from several different coated and uncoated DW optical surfaces was monitored. For uncoated samples, the backward scatter losses are in good agreement with the predictions of scalar scattering theory, indicating that in this case scattering is mainly determined by surface effects. Although forward and backward scatter losses are of the same order of magnitude for uncoated samples, they differ by up to two orders of magnitude for high-reflection- and by one order of magnitude for anti-reflection-coated samples. The experimental data demonstrate that the anti-reflection coatings suffer from substantial losses due to forward scattering, whereas backward scattering is the predominant loss channel for high-reflection coatings. In addition, the strong influence of defects and impurities on the total scattering is demonstrated.

Absorption of thin Al2O3 films was measured at 193 nn with an ArF-laser calorimeter. In addition to the expected high linear absorption coefficient, we found, for the first time to our knowledge, that two-photon absorption and transient color-center formation are nonnegligible loss channels in thin films at 193 nm. The nonlinear absorption coefficient is of the order of several times 10(-4) cm/W. (C) 2000 Optical Society of America. OCIS codes: 310.6860, 310.1620, 260.7190.

Linear and nonlinear absorptance in Al2O3 films of different optical thicknesses are investigated using an ArF laser calorimeter. While the linear absorptance at 193 nm shows the expected linear increase, nonlinear absorptance increases quadratically with increasing film thickness. Thus, it cannot be described by a constant nonlinear absorption coefficient beta. The experimental findings are explained by a simple phenomenological approach using excited states with a finite interaction length longer than the actual film thickness, a new material constant Gamma is introduced, which describes the nonlinear absorptance behavior correctly.

We report on the fabrication of periodic nanostructures on selected materials by short-pulse uv-laser ablation. Temporal studies reveal details of the ablation process with subpicosecond time resolution. Biochemical applications of the nanostructures for planar waveguide technology are presented.