Imaging of high harmonic radiation emitted during the interaction of a 20 TW laser with a solid target

We present images of the source of extreme ultraviolet (XUV) harmonic emission at a wavelength of 220 Å from the interaction of a 20 TW, 1.053 μm Nd:glass laser beam focused to intensities up to 4×1018 W cm−2 onto a solid target. From these measurements we determine an upper limit to the source size and brightness of the harmonic emission to show its efficacy as a novel source of short-pulse, coherent XUV radiation. We also demonstrate the empirical scaling of the harmonic generation efficiency with irradiance up to 1019 W μm2 cm−2, and extrapolate to estimate the possible source brightness at higher irradiances. These source brightnesses are compared to those available from an x-ray laser system.