Among quasi-phase matching (QPM) materials, PPLN suffers from a limited transparency, strongly limiting both the output power and the beam quality above 4 μm. We are developing a new QPM technology based on Orientation- Patterned Gallium Arsenide (OP-GaAs) crystals, transparent up to 16 μm and showing excellent nonlinear and thermal properties and very low losses (<0.02 cm-1). We demonstrated with such samples a high-repetition rate tunable OPO attractively pumped by a remote Thulium fiber laser and integrated in a 25×30×6 cm transportable head. A 3 W level output in the 3-5 μm range was obtained with a 53% efficiency and an unprecedented beam quality (M2=1.4), making this module most suited to study directed infrared countermeasures (DIRCM).© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.