High Average Power Second-harmonic Generation of a CW Erbium Fiber MOPA

We report the generation of 28 W of 780 nm radiation with near diffraction limited beam quality (M²≤1.15) by frequency-doubling a continuous-wave (CW) erbium fiber master oscillator power amplifier (MOPA) system in a periodically poled lithium niobate crystal. The second-harmonic generation conversion efficiency reached 45% with no roll-off observed, suggesting that further power scaling should be possible with higher fundamental pump powers. The generated second-harmonic had a 3 dB spectral bandwidth of 0.10 nm. The presented architecture represents a simple and effective route to generating high-brightness radiation around 780 nm