Watt-level, gigahertz-linewidth difference-frequency generation in PPLN pumped by an nanosecond-pulse fiber laser source

We obtained >1 W average power and up to 5 μJ pulse energy at ∼3520 nm wavelength via difference-frequency generation (DFG) of an all-fiber, few-ns pulse, variable pulse-repetition-frequency laser source operating at 1064 nm and 10 mW, continuous-wave, 1525 nm single-frequency diode laser, within a 5 cm-long periodically poled lithium niobate (PPLN) crystal. To the best of our knowledge, this result amounts to the highest-average-power, spectrally bright mid-infrared radiation obtained via DFG.