Experimental Investigation on 1018-nm High-Power Ytterbium-Doped Fiber Amplifier

We present an all-fibered 1018-nm ytterbium-doped double-clad fiber laser in master oscillation power amplification configuration. The output characteristics of 1018-nm laser with seed power, gain fiber length, and fiber type are experimentally investigated. The power of the seed laser needs to be much higher to suppress amplified spontaneous emission and enable the sufficient amplification of the 1018-nm seed laser than the case of 1080-nm amplification. And the requirement of the seed power increases with the gain fiber length. The experimental results also indicate that gain fiber with large pump fill factor and low Yb ion concentration is more appropriate for the high-power 1018-nm fiber laser. With this gain fiber, we demonstrate a 77-W near diffraction limited fiber amplifier emitting at 1018 nm with power conversion efficiency of 75%.