High-power extra-large-mode-area Yb-doped fiber laser and amplifier at 978 nm

We report an efficient, high-power operation of a fiber laser and a power amplifier at ~ 978 nm incorporating an extra-large-mode-area (XLMA) triple-clad Yb-doped fiber. A simple numerical calculation for the gain of the XLMA Yb fiber shows that robust operation near 978 nm can be achieved due to the high Yb3+ excitation density in the XLMA Yb fiber with a relatively large core-to-cladding area ratio. The XLMA Yb fiber laser in a simple free-running configuration is constructed, yielding 38 W of continuous-wave (cw) output at 978 nm. Moreover, the single-stage XLMA Yb fiber power amplifier, employing the laser diode as a seed source, successfully produced 77 W of the amplified output at 977.2 nm without significant amplified spontaneous emission or parasitic lasing. The prospects for power scaling and applications are considered.