Abstract:
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.