The use of Fe:ZnSe polycrystals as passive Q-switches for the Er:Cr:YSGG laser operating at 2.8&mgr;m is introduced.
Fe:ZnSe samples with 1-7cm-1 coefficients of absorption were prepared using thermal diffusion of iron in CVD grown
polycrystalline ZnSe. A flashlamp pumped Er:Cr:YSGG laser with a variable (40 - 80% reflectivity) output coupler (OC)
was used as a test bed for passive Q-switching. Using a 90% initial transmission Fe:ZnSe placed at the Brewster angle
we obtained a single giant pulse lasing with a pulse duration of ~65 ns and a maximum output of 13 mJ under 30 J of
flashlamp pump. Multi-pulse (19 pulses) output was obtained with 85 mJ total output energy at a pump energy of 30 J.
The saturation curve of Fe:ZnSe was measured. Fitting this data with a theoretical model results in absorption crosssection
of 0.56 × 10-18 cm2, which is close to the value of the absorption cross-section obtained from spectroscopic
measurements (0.85 × 10-18 cm2 at 2.8 &mgr;m).