A Sub-Picosecond Source of Coherent, Partially Tunable, VUV Radiation Operating at High Repetition Rate

We report the realization of a VUV radiation source based on high order harmonic generation in gases. High pulse repetition rate, tunability, spatial and temporal coherence, short pulse duration and, in turn, extremely high brightness and considerable average photon fluxes are some of its characteristics which make it very feasible for spectroscopy, ultrafast processes and surface physics experiments. We observed up to the 13th harmonic (λ ≈ 61 nm) of a Ti:Sa laser (λ, ≈ 800 nm), operating at 1 kHz repetition rate, after its interaction with a Xe gas target. In spite of the low pulse energy (≈ 1 mJ) of the Ti:Sa source, intensity in excess of 1014 Wcm-2 can be easily obtaitened due to the short pulse duration (≈ 100 fs) and the good optical quality of the laser beam, which allows its focusing near the diffraction limit. At such intensity level, odd harmonics of the laser fundamental frequency are produced up to very high orders1. We report here the spectrum of VUV radiation generated during the laser-gas interaction and a study of the spectral profile of the 9th harmonic.