VUV lasers pumped by diffuse discharges

Parameters of stimulated emission in diffuse discharges formed in a sharply inhomogeneous electric field by run-away electrons in mixtures of rare gases with additions of hydrogen and fluorine at pressures up to 10 atm are studied. Efficient VUV lasing was obtained at wavelengths from 148 to 193 nm on the transitions of hydrogen, fluorine and exciplex ArF* molecules. It was shown that the addition of helium buffer gas increases the pulse duration, while neon addition improves output energy of VUV laser on H 2 Lyman band. The laser pulse duration over 10 ns and the output of 0.12 mJ were obtained. The diffuse discharge in mixtures of He with F 2 was found to form by successive ionization waves. It was shown that laser pulse at 157 nm has three peaks, which correspond to the maxima of the diffuse discharge current. Therewith the first or second peak of laser radiation has the maximum intensity depending on the amplitude of the conduction current in the primary ionization wave. Maximal F 2 * laser electrical efficiency of η 0 = 0.18% and the output of Q 157 = 3.8 mJ were obtained in a He–F 2 gas mixture at pressure of 10 atm which exceeds the efficiency of lasers of this type pumped by transverse volume discharges with UV preionization. Long-pulse operation of ArF* laser was achieved in He–Ne–Ar–F 2 gas mixture. Lasing at 193 nm continued during two periods of the diffuse discharge current. Total duration of the laser pulse was as long as 40 ns, and the radiation energy at 193 nm was as high as 2 mJ from an active volume of 20 cm 3 .