HARMONIC-GENERATION IN AN IONIZED-GAS MEDIUM WITH A 100-FEMTOSECOND, HIGH-REPETITION-RATE LASER SOURCE AT INTERMEDIATE INTENSITIES

We report the realization of a vacuum-ultraviolet radiation source bas ed on high-order harmonic generation in noble-gas samples, operating a t high repetition rate. In particular, we observed up to the 13th harm onic (lambda = 61 nm) of the fundamental frequency of a short pulse, h igh repetition rate titanium-sapphire laser after its interaction with a Xe gas jet. The effects of the propagation of the fundamental and h armonic beams through an ionized medium are studied by analysing the s pectral profile of the 9th and 7th harmonics. Finally, we report a stu dy of the dependence of the harmonic conversion efficiency on relative position of the focus and the gas target.