Generation of vacuum ultraviolet radiation by sum frequency mixing of a femtosecond and a nanosecond laser

The interaction of high-intensity short pulse (fs) lasers with atomic or mo lecular vapors permits the conversion of visible light to intense coherent radiation in the vacuum ultraviolet spectral region. We demonstrate sum fre quency mixing of a high-intensity short pulse (fs) laser with a conventiona l long pulse (ns) laser to extend the accessible wavelength range of harmon ic generation. The mixing process does not rely on meeting resonances and c an in principle be implemented with any intense short pulse (fs) laser syst em in any nonlinear medium. The efficiency of the sum frequency mixing proc ess is comparable to the efficiency of harmonic generation of a similar wav elength with the high-intensity short pulse (fs) laser alone. We propose th e application of conventional tunable long pulse (ns) lasers to permit the generation of broadly tunable picosecond radiation in the vacuum ultraviole t. (C) 2000 Published by Elsevier Science B.V.