Femtosecond parametric generation in ZnGeP_2

We report traveling-wave optical parametric generation in short (2-mm) ${\mathrm{ZnGeP}}_2$ samples with reduced anomalous absorption, using femtosecond pump pulses near $2 \mu \mathrm{m}$. The signal and the idler waves generated could be tuned from 2.5 to $10 \mu \mathrm{m}$, and they extend the tunability of the $\beta$-barium borate optical parametric generator used as a pump source to the mid-infrared. At a single-pass internal conversion efficiency of 2.5% we estimate pulse durations of 75 fs (signal near $3 \mu \mathrm{m}$) and 200 fs (idler near $6 \mu \mathrm{m}$).