Narrowband tunable VUV radiation generated by nonresonant sum- and difference-frequency mixing in xenon and krypton.

Nonresonant sum- and difference-frequency mixing of the fundamental omega(L) and the second harmonic omega(UV) radiation of a powerful narrowband pulsed dye laser system excited by an Nd:YAG laser (lambda(L) = 5500-6500 A) generates intense VUV radiation in krypton and xenon with the frequency omega(VUV) = 2omega(UV) micro omega(L). The sum-frequency is tunable in spectral regions of negative dispersion between 1100 and 1300 A. The maximum VUV pulse power exceeds 20 W (5 x 10(10) photons/pulse). VUV light pulses with up to 60 W (2.3 x 10(11) photons/pulse) are provided by the difference-frequency at wavelengths between 1850 and 2070 A. In addition the conversion process omega(VUV) = 2omega(UV) - omega(IR) (omega(IR) is the frequency of the Nd:YAG laser) generates radiation in the wavelength range of 1595-1866 A. With present laser systems the tuning range of the difference-frequency could be extended to wavelengths as short as 1226 A. The sum- and difference-frequency conversion will thus provide intense coherent VUV light continuously tunable between 1100 and 2100 A.