Preionization of XeF excimer laser by 248 nm laser beam

A new type of preionization setup for a XeF excimer laser was investigated. The laser gas was ionized using a 248 nm laser beam. The preionization laser beam follows the optical axis of the XeF laser resonator thereby ionizing the laser gas. The timing of the ionizing beam with respect to the main discharge has a great influence on laser output energy and stability. To achieve optimum performance the preionization laser pulse should occur about 90 ns prior to the ignition of the main discharge of the XeF laser. The optimal energy density of the preionization beam was found to be around 10 mJ/cm(2). By direct comparison to a standard preionization setup using a corona discharge along the main discharge region, the pulse energy of the XeF laser could be increased. However, the stability could not be improved.