Investigations of the brightness of high order harmonics generated by intense laser interactions with solid and gaseous targets

This thesis presents an experimental investigation into the brightness of high harmonic radiation produced during the interaction of high power lasers with both gaseous and solid targets. High harmonics of optical and UV (ultraviolet) lasers represent one of the most favourable ways of generating short pulse coherent radiation in the extreme ultraviolet (XUV) region of the electromagnetic spectrum. For harmonics produced via gas target interactions the yield is optimised for wavelengths between 35 and 11 nm generated from a many times diffraction limited 248 nm UV laser. The results show over an order of magnitude improvement on previous measurements even for these non-optimal laser conditions. Good agreement to the data is found with code simulations which show possibilities for further increases in brightness at these and shorter wavelengths from a better quality laser driver. From a 1.053 #mu#m laser-solid target interaction experiment the first ever measurement of the harmonic brightness is presented. Using simple scaling laws the expected brightness at higher laser intensities is inferred, and possible methods of improving the source parameters with improved laser conditions are discussed. A comparison is then made of the relative brightness of the harmonics produced via the gaseous and solid target interactions and with current X-ray lasers. Finally an experimental feasibility study is presented utilising a 248 nm UV driving laser for solid target harmonic generation. These results show good agreement with code simulations including appropriate plasma conditions. (author)SIGLEAvailable from British Library Document Supply Centre-DSC:D203749 / BLDSC - British Library Document Supply CentreGBUnited Kingdo