Continuous-wave 4.3-mu m intracavity difference frequency generation in anoptical parametric oscillator

We have achieved 150 mW of cw output at 4.3 mum, using difference frequency mixing in a singly resonant optical parametric oscillator (OPO). We pumped the OPO cavity, which contains periodically poled LiNbO3 (PPLN), with a 14 -W 1.06-mum Nd:YAG laser to generate a signal at 1.7 mum and an idler at 2. 8 pm Mixing of the two waves at the same crystal temperature and grating sp acing yielded emission in the mid IR. This technique avoids the mid-IR abso rption-high-threshold problem, which has limited the cw performance of PPLN OPO's at wavelengths beyond 4 mum. Provided that tunability is not require d, this method is a simple alternative to multiple-crystal configurations. (C) 2001 Optical Society of America OCIS codes: 140.3070, 140.580, 190.2620 , 190.4970, 190.4860.