GENERATION OF INTENSE PICOSECOND PULSES TUNABLE BETWEEN 1.2-MU-M AND 8.7-MU-M

We demonstrate that a parametric set-up consisting of three LiNbO3 crystals pumped by the output of a picosecond Nd:YAG laser can easily be extended so that wavelengths between 1.2 and 8.7-mu-m can efficiently be generated. This extension consists of an extra LiNbO3 crystal and an AgGaS2 crystal. In the LiNbO3 crystal the idler generated by the parametric set-up is frequency doubled. The doubled idler is used as a seed for parametric amplification in the AgGaS2 crystal pumped by the Nd:YAG. In this way the doubled idler between 1.2 and 1.4-mu-m is strongly amplified and a strong pulse at the difference wavelength between 4.5 and 8.7-mu-m is generated. The maximum energy-conversion efficiency is 5.4%. With this set-up we can generate pulses with a pulse duration between 15 and 20 ps that are continuously tunable from 1.2 to 8.7-mu-m.