Limitations and perspectives in power scaling of fiber lasers (Invited Paper)

Fiber lasers are reliable and flexible sources of high laser power with excellent beam quality. However, limitations due to nonlinear and thermal effects, hamper further power scaling. We will give an overview over relevant influencing factors for these limitations, on the component side as well as regarding system design. Experimental examples in the 1µm and 2µm spectral region will be shown for the proposed techniques to tackle several of these obstructions, with a focus on ways to suppress transverse mode instabilities. Remaining limitations for single fiber systems can be overcome by parallelization of amplification, using multiple actively doped cores running below the critically power threshold each. Such fiber cores can be housed separately or in a single multi-core fiber. We will address coherent and spectral methods to (re-)combine multiple fiber laser output beams while maintaining beam quality and discuss scaling aspects and potential limitations to these architectures.