Thermally guided Yb-doped fiber-rod amplifier and laser

In this paper, we describe a thermally guided fiber-rod amplifier and laser oscillator, which exploit thermal guiding to achieve mode control. This power scalable approach operates with mode sizes that are typically an order of magnitude larger than traditional single-mode fibers. Operating as an amplifier, we achieve a small-signal gain of 5 dB at 1030 nm whilst maintaining excellent beam quality ( M 2 < 1.1). In a laser configuration, we obtained 13.1 W of diffraction-limited ( M 2 < 1.1) output power at 1032.5 nm, with a slope efficiency 53% with respect to absorbed power. A model predicting beam evolution through the thermally guided fiber-rod gain medium is presented and validated.