Radiation effects of an ArF excimer laser in alkali iodide crystals

Radiation effects of an ArF excimer laser (193 nm) have been studied for tw o kinds of samples of alkali iodides. One is the usual bulk crystals and th e other the thin crystals grown in a small gap of two quartz plates. After irradiation, we have found a remarkable striped pattern in both samples by a microscope. The pattern is well interpreted in terms of the light intensi ty distribution of the Fresnel diffraction induced by a knife edge. The mic roscopic mechanism of the appearance of the pattern is discussed on the bas is of the Raman scattering spectra of both samples.