Generation of widely tunable harmonic pulses in the UV and VUV from a NIR optical parametric amplifier

We demonstrate the generation of tunable high-order harmonics from the inte raction of the signal output of a near-infrared (NIR) traveling-wave optica l parametric amplifier (OPA) with the xenon atoms of a pulsed gas jet. By t uning the OPA between 1200 and 1550nm, we generate widely tunable pulses of ultraviolet radiation up to the ninth harmonic order, around 150 nm. The p ossibility to cover the VUV region thanks to the full overlap of the tunabi lity ranges of different harmonic orders below 220 nm is also proved.