Femtosecond sum-frequency generation in KB/sub 5/O/sub 8//spl middot/4H/sub 2/O down to 166 nm

Summary form only given. Previous experiments with LBO permitted the generation of up to now the shortest wavelength of 172.7 nm in the vacuum ultraviolet (VUV) with an all-solid state laser system by mixing the fourth harmonic (FH) from a Ti:sapphire regenerative amplifier and the idler wave from an optical parametric generator. Although reports on a number of new borates appeared since then, they do not seem to possess the necessary advantages over LBO to move to even shorter VUV wavelengths. In the present work we demonstrate that such sum-frequency generation (SFG) is possible in the well known material KB/sub 5/O/sub 8//spl middot/4H/sub 2/O (KB5) which is transparent down to 162 nm. The important advantage of KB5 over LBO is that the effective nonlinearity is maximized for propagation along the y-axis where the shortest SFG wavelengths are produced, whereas that of LBO vanishes there. This, in combination with the larger birefringence of KB5 allowed us to generate /spl ap/200 fs pulses in the 166-172 nm spectral range. To the best of our knowledge this is the first demonstration of an all solid state laser system operating so deep in the VUV.