COHERENT EXTREME-ULTRAVIOLET GENERATION AT 64 NM BY EFFICIENT FREQUENCY TRIPLING OF AN ARF LASER

Third-harmonic (TH) generation for an ArF excimer laser in a hydrogen (H-2) gas jet was investigated. When the ArF laser radiation was tuned into a two-photon resonance in H-2, enhanced efficiency for TH was ob served. 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. Absolu te TH energy of similar to 1-mu J pulse was measured by two different methods. The proposed narrow-band extreme-ultraviolet source with a co mmercial excimer laser with a high repetition rate should be useful no t only for scientific applications but also for industrial application s such as laser processing. (C) 1997 Optical Society of America.