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

Ž . The interaction of high-intensity short pulse fs lasers with atomic or molecular vapors permits the conversion of visible light to intense coherent radiation in the vacuum ultraviolet spectral region. We demonstrate sum frequency mixing of a Ž . Ž . high-intensity short pulse fs laser with a conventional long pulse ns laser to extend the accessible wavelength range of harmonic generation. The mixing process does not rely on meeting resonances and can in principle be implemented with any Ž . intense short pulse fs laser system in any nonlinear medium. The efficiency of the sum frequency mixing process is Ž . comparable to the efficiency of harmonic generation of a similar wavelength with the high-intensity short pulse fs laser Ž . alone. We propose the application of conventional tunable long pulse ns lasers to permit the generation of broadly tunable picosecond radiation in the vacuum ultraviolet. q 2000 Published by Elsevier Science B.V.