Third-harmonic (TH) generation for an ArF excimer laser in a hydrogen gas jet was investigated. When the ArF laser radiation was tuned into a two-photon resonance in , enhanced efficiency for TH was observed. Optimum experimental conditions of efficient TH generation for our apparatus such as gas-jet density and energy fluence of the laser were obtained. Calculation of the phase-matching condition including absorption led to an optimum gas-jet profile for TH generation. Absolute TH energy of -µJ pulse was measured by two different methods. The proposed narrow-band extreme-ultraviolet source with a commercial excimer laser with a high repetition rate should be useful not only for scientific applications but also for industrial applications such as laser processing.
© 1997 Optical Society of America