Study of the structure and parameters of a KrF excimer laser beam

For a KrF excimer laser with a confocal unstable resonator, energy distribution over the beam cross-section was measured with the aid of luminescence in the glass induced by the UV laser radiation. A complex fine structure of the beam has been found. In an area close to the focus, measurements were carried out by means of two different methods-via thermal paper blackening and via ablation craters on a glass surface. The complex beam structure above has been shown to persist also in the immediate vicinity of the beam waist. Measured cross-sectional waist dimensions varied significantly within a range from 0.3 to 0.6-1.3 mrad depending on the measuring procedure applied. Using a short-focus nonaberrational lens one could obtain a focal spot with linear dimensions of several tens of micrometers.