Spatial coherence of KrF excimer lasers

The spatial coherence and the beam divergence at 248 nm of a KrF excimer laser were obtained experimentally. These results are in good agreement with the theoretical calculations based on a simple pulse-laser model and the van Cittert-Zernike theorem. The relation between the spatial coherence and the beam divergence was obtained theoretically and supported by experimental results. This expression is given as a function of the wavelength of the laser but includes no parameters related to the laser structure. It is shown that these theoretical results are applicable to various kinds of pulse laser.