Edge steepness and plateau uniformity of a nearly flat-top-shaped laser beam

Abstract

We present experimental results of reshaping and making uniform the spatial energy distribution of a raw beam emitted by a large-aperture (10 cm×5 cm) excimer laser. To this end, we use an optical system that is able to homogenize “bad beams” having strong local intensity spikes, and to modulate almost continuously the spot size of the homogenized beam along one or both axes in a fixed target plane. We evaluate the results using the standard parameters described in the ISO 13694:2000 document of the International Organization for Standardization. We find that the reliability of the results is dependent both on the experimental setup and on the definition of the edge steepness and plateau uniformity of the quoted ISO document. Here we propose an amendment to the definition of these standard parameters that could improve their reliability.