Tunable coherent far-UV generation by frequency conversion in BBO

Tunable vacuum ultraviolet radiation below 200 nm was generated in a beta barium borate (BBO) crystal by noncollinear sum-frequency mixing (SFM) of Nd:YAG laser radiation and the second harmonic of a dye laser pumped by the third harmonic of the neodymium laser. The lower limit attained was 187.9 nm, being the shortest wavelength generated in the crystal to date. The tunability was extended, up to 230 nm, in BBO by generation of the third harmonic (SFM of the second harmonic with the fundamental) of the dye laser pumped by the second harmonic of the Nd:YAG laser. An SFM conversion efficiency as high as 21% was achieved when the energy of the fundamental dye-laser beam was only 10 mJ.