Two-photon-resonant difference-frequency mixing with am ArF excimer laser:vacuum-ultraviolet generation and multiphoton spectroscopy

Two-photon-resonant difference-frequency generation using an ArF excimer la ser provides widely tunable vacuum-ultraviolet (VUV) radiation at high puls e energies. Two-photon resonances in H-2, Kr, and Hd are within the tuning range of the ArF laser. With this technique we have directly measured > 65 muJ at 133 nm. H-2 has a significantly smaller phase mismatch than Kr, lead ing to more efficient VUV generation, particularly at shorter VUV wavelengt hs. However, mixing in H-2 also produces additional VUV lines from two-phot on excited amplified spontaneous emission. We have observed new amplified s pontaneous-emission lines produced in this manner. H-2 is ineffective at ge neration of Lyman-alpha radiation owing to the production of H atoms. With a phase-matched mixture of Kr and Ar, we have directly measured 7 muJ at Ly man-alpha. A physical basis for the asymmetric tuning profile in this gas m ixture is presented. With light from this VUV source we have performed 1+1 resonantly enhanced multiphoton ionization in Xe at 147 nm and two-photon-e xcited fluorescence in Ne at 133 nm. (C) 2000 Optical Society of America [S 0740-3224(00)00810-9].