Frequency conversion of femtosecond Ti:sapphire laser pulse to the long-wave mid-IR range with BaGa$_2$GeSe$_6$ crystal

Generation of ultrashort mid-IR pulses spanning from 8.5 to 10.5 $\mu$m with high energy (up to 4.5 $\mu$J) was experimentally demonstrated through difference frequency generation in BaGa$_2$GeSe$_6$ crystal pumped by 100-fs 0.95-$\mu$m Ti:sapphire laser pulses. Optical damage threshold and two-photon absorption coefficient were determined for this pump pulses. Frequency conversion efficiency reached 0.24% at 1.85 mJ pump pulse energy and was decreased at higher one. Estimations indicate that application of 15 mm in diameter wide-aperture BaGa$_2$GeSe$_6$ sample will allow one to increase pump pulse energy up to $\sim$ 10 mJ, and to increase the mid-IR pulse energy up to 24 $\mu$J at the same efficiency.