We report a master-oscillator fiber power-amplifier system consisting of a diode-pumped monolithic nonplanar ring laser as the master oscillator and a Yb-doped large-mode-area double-clad fiber as the power amplifier. The system emits up to 20.1 W of single-frequency radiation at a wavelength of 1064 nm with diffraction-limited beam quality (M<sup>2</sup>≤1.3) . The optical emission spectrum and amplitude-noise behavior are investigated. Furthermore, the power-scaling possibilities are discussed.
© 2001 Optical Society of America
S. Höfer, A. Liem, J. Limpert, H. Zellmer, A. Tünnermann, S. Unger, S. Jetschke, H.-R. Müller, and I. Freitag, "Single-frequency master-oscillator fiber power amplifier system emitting 20 W of power," Opt. Lett. 26, 1326-1328 (2001)