mW-class continuous-wave mid-infrared generation in the 4-μm region by using difference frequency generation with a MgO-doped PPCLN crystal

A mW-class continuous-wave single-frequency tunable mid-infrared beam was produced at 4 μ m via difference frequency generation (DFG) of two near-infrared beams at about 850 nm and 1056 nm. The pump and the signal beams of 1Wand 5.5 W, respectively, are incident onto a MgO-doped periodically-poled congruent lithium-niobate crystal (MgO-doped PPCLN) for the DFG process. This system produces an idler beam with powers of approximately 0.95 mW at 4.47 μ m and 1.9 mW at 4.0 μ m. We investigate the mid-infrared beam characteristics, such as the power, beam quality, tuning range and so on.