Resonant sum and difference frequency mixing in Hg

Coherent tunable VUV radiation of narrow spectral width is generated by two-photon resonant sum and difference frequency mixing of pulsed dye laser radiation in Hg vapor. The UV frequency ωuvis tuned to the two-photon resonances 6¹S0- 7¹S0( Å), 6¹S0-6¹D2( Å), and 6¹S0- 7¹D2( Å). A second dye laser produces tunable radiation at ωD( Å). At input powers of 1-2 MW, the different conversion schemes generate VUV light pulses of typically 0.5-3 kW in spectral regions between 1090 and 1960 Å. The experimental results provide information on the wavelength dependence of the generated VUV output, on the conversion efficiency, the phase-matching conditions, and on conversion limiting saturation phenomena. Besides the resonant frequency conversion, nonresonant frequency tripling and mixing is investigated at Å in the vicinity of the resonance transition 6¹S0-6¹P1( Å).