High-Power, Continuous-Wave, Fiber-Pumped Difference-Frequency-Generation at 2.26 μm

Abstract

We report a high-power source of continuous-wave (cw) mid-infrared (mid-IR) radiation at 2.26 μm based on difference-frequency-generation (DFG) of a cw Yb-fiber laser at 1.064 μm and a cw Tm-fiber laser at 2.010 μm in MgO:PPLN. Using a 50-mm-long crystal with a single grating period of 32.16 μm and a simple single-pass setup, we generate up to 3.84 W of cw output power at 2.26 μm at a power conversion efficiency of ~0.47%/W. The DFG output beam is characterized by a Gaussian TEM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</sub> spatial profile with M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> <; 1.2, and exhibits excellent passive power stability of 0.6% rms and spectral stability better than 0.01% over 1 hour. We find close agreement between the measured conversion efficiencies and theoretical predictions, confirming optimum performance of the DFG source. Our approach represents a viable and practical alternative to the existing methods for generating this useful wavelength. To the best of our knowledge, the generated output represents the highest cw power obtained from any single-pass nonlinear frequency conversion source in the mid-IR.