A Long Pulse Discharge Excited ArF Laser

An X-ray preionised, discharge excited ArF excimer laser, = 193 nm, has been studied in the long pulse regime. The laser performance is found to be primarily dependent on the discharge stability, and therefore, on the gas composition, preionization timing and the pumping power. Using X-ray preionization and prepulse-mainpulse excitation, laser pulselengths of up to 120-ns full-width at half-maximum at 4 mJ/` are obtained by decreasing the partial pressures of the active ingredients, F2 and Ar, and using Ne as a buffergas. This is almost six times as long as usual for discharge excited ArF lasers.