High-power mid-infrared ZGP optical parametric oscillator directly pumped by pulsed Tm:YLF laser at 1908 nm

This paper presents the first demonstration of a mid-infrared optical parametric oscillator (MIR OPO) based on ZGP crystal which was directly pumped by an acousto-optical Q-switched Tm:YLF laser at 1.908 μm. Profited from the improved quality of ZGP crystal with low absorption coefficient (<0.04 cm−1) and high laser-induced damage threshold (>3 J/cm2) at 1.908 μm, output power of 17.8 W for both the 3.53 μm signal and 4.15 μm idler lasers was achieved when the double-pump-pass, doubly-resonated ZGP OPO was pumped at 28.6 W. To the best of our knowledge, this is the highest output power and efficiency for any kind of Tm-laser directly-pumped OPOs.