Output characteristics of an excimer laser with delayed double preionisation

The authors present the output characteristics of an excimer laser (XeCl and KrCl) with delayed double UV preionisation. He- and Ne-based mixtures were used for the XeCl laser and Ne-based mixtures for the KrCl laser, at pressures up to 7*10 5 Pa. For both lasers, maximum output energies (1.1 J/pulse at 308 nm and 0.3 J/pulse at 222 nm) were obtained for a delay time of about 290 ns between the onset of the preionisation and the breakdown of the laser gas. At a charging voltage of 50 kV, by varying the delay time from 140 ns to 290 ns, an improvement in the output energy of 16% for the XeCl laser and 22% for the KrCl laser was obtained. The improvement in respect of a single preionisation is about 18% for the XeCl laser with the He-based mixture, and about 14% for the XeCl laser with the Ne-based mixture.