Record-efficiency mid-IR generation from all-fiber-pumped ZGP and CSP OPOs

ZnGeP₂ (ZGP) and CdSiP₂ (CSP) for high-power mid-infrared (mid-IR) generation in the 3–5 µm range. The system is pumped by an actively pulse-shaped fiber MOPA at 2048 nm delivering pulses with 1.5 mJ pulse energy. The ZGP OPO achieves 25.8 W mid-IR power with 69% conversion efficiency, while the CSP OPO reaches 13.3 W at a 48% conversion efficiency. Both systems show stable, power-scalable operation without any signs of roll-off. This work demonstrates the first all-fiber-pumped CSP OPO and achieves the highest published conversion efficiency for CSP OPOs above 2.5 W mid-IR output power, as well as the highest conversion efficiency among all watt-level mid-IR ZGP OPOs to date.