GENERATORS AND MODE-LOCKED OPTICAL PARAME TRIC-AMPLIFIERS

Light sources tunable in the visible and IR with pulse durations of a few picoseconds can be realised using the third harmonic of a modelock ed Nd:YAG laser and performing several parametric generations and ampl ifications in BBO crystals. The performances of such a setup are very satisfying, only the spatial and spectral quality of the beam has to b e improved: A spatial filtre technique using an optical fiber of a cor e-diameter of 5 mu m can be employed. The resulting light source is tu nable between 0,4 and 2,5 mu m, it has an almost perfect spatial Gauss ian profile, a pulse duration of 20 ps and a spectral width of less th an 0.9 cm(-1) at a wavelength of 870 nm. This yields an excellent band with product Delta nu Delta t of 0.5, which is only 1.1 times the Four ier limit for spectral Gaussian pulses. The maximum output energy was measured to be 2 mJ per pulse with a pump pulse energy of 15 mJ.