We report on reflection gratings produced entirely of dielectric materials. This gives the opportunity to enhance the laser damage threshold over that occurring in conventional metal gratings used for chirped-pulse-amplification, high-power lasers. The design of the system combines a dielectric mirror and a well-defined corrugated top layer to obtain optimum results. The rules that have to be considered for the design optimization are described. We optimized the parameters of a dielectric grating with a binary structure and theoretically obtained 100% reflectivity for the -1 order in the Littrow mounting for a 45 degrees angle of incidence. Subsequently we fabricated gratings by structuring a low-refractive-index top layer of a multilayer stack with electron-beam lithography. The multilayer system was fabricated by conventional sputtering techniques onto a flat fused-silica substrate. The parameters of the device were measured and controlled by light scatterometer equipment. We measured 97% diffraction efficiency in the -1 order and damage thresholds of 4.4 and 0.18 J/cm(2) with 5-ns and 1-ps laser pulses, respectively, at a wavelength of 532 nm in working conditions.

Recent measurements of Lindhard's scattering function are used as starting point for some theoretical investigations of the elastic atom-atom scattering within the quasistatic model. Good agreement is found for scattering of light ions on heavy atoms. For heavy collision partners the theoretical results agree in average with the experiments but don't provide the oscillations in full magnitude. This deviation is caused by neglecting the deformation of electron distributions.Ausgehend von neueren Rlessungen der Lindhardschen Streufunktion werden einige theoretische Untersuchungen zur elastischen Atom-Atom-Streuung im Rahmen des quasistatischen Modells gemacht. I m Falle der Streuung leichter lonen a n schweren Atomen wird eine gute Ubereinstimmung erhalten. Fur schwere StoSpartner stimmen die theoretischen Ergebnisse im Mittel mit den Experimenten uberein, liefern jedoch zu sehwache Oszdlationen. Diese Abweichung entsteht durch das Vernachlassigen der Deformation der Elektronenverteilungen.

Measurements of optical transmission and Rutherford backscattering experiments (RBS) are carried out to investigate the correlation between different defect structures and the near edge optical properties of nitrogen implanted GaAs. The defect structures detected with these methods can be classified into two groups. A point defect‐like structure connected with an exponential long tail to the absorption edge and a weak contribution to the dechanneling without any damage peak in the RBS spectra preferably occurs for low dose implantation at Ti = 80 K and for room temperature implantation. A transition to heavily damaged regions connected with a short tail to the absorption edge is formed for higher fluences at Ti = 80 K. In this case damage peaks occur in the RBS spectra and the refractive index change reaches a value of about 10% after formation of a continuous amorphous layer.

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