VACUUM-ULTRAVIOLET APPLICATION OF LI2B4O7 CRYSTALS - GENERATION OF 100 FS PULSES DOWN TO 170 NM

We investigate and characterize the newly grown crystal Li2B4O7 which is transparent down to 160 nm for nonlinear optical conversion into th e vacuum ultraviolet using sum frequency mixing with femtosecond pulse s. This material exhibits excellent properties below 180 nm and makes possible the generation of wavelengths down to 170 nm with an all soli d state laser system. The most important advantage of Li2B4O7 in this spectral range turns out to be the possibility of utilizing noncritica l phase matching with maximized effective nonlinearity. We demonstrate generation of nearly transform limited 100 fs pulses between 170 and 185 nm with conversion efficiency of 4%. Their peak powers range from 200 kW at 170 nm >2 MW at 185 nm. (C) 1998 American Institute of Physi cs. [S0021-8979(98)07523-9]