This paper presents a new frequency conversion architecture based on a cascaded KTiPO4 (KTP) and ZnGeP2 (ZGP) optical parametric oscillator (OPO)/optical parametric amplifier (OPA) system. Up to 0.84 W of combined signal and idler output is achieved, which is tunable across the 3.8-4.8 μm spectral region. Incident Nd:YAG pump power is 6.3 W. To achieve efficient low pulse energy conversion, the KTP OPO used a line focus and multiple crystal walk-off compensation. The novel ZGP OPO/OPA configuration efficiently utilizes both of the orthogonally polarized KTP OPO signal and idler beams. The OPA is pumped by combining the 3.8-4.8 μm output from the ZGP OPO with the unused 2.13 μm beam, which is then focused into two ZGP crystals configured as a walk off compensated OPA. Measured beam quality of the OPA signal and idler output has an M2<2, and the residual 2.13μm OPA pump light is also collinear with the mid-IR light.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.