Abstract
In recent experiments of high-performance two micron ultrafast fiber-laser systems rather unexpected effects have been observed, which challenge peak as well as average power scaling in this interesting spectral region around 1.9 μm [1]. These effects can be associated with the propagation in ambient air (in this case with water-vapor absorption lines) and they affect both the quality of the pulse profile in the temporal domain [2] and the spatial confinement of the beam profile [3]. Although these effects have been known for several decades, they have, to the best of our knowledge, not yet been studied in context with peak and average power scaling of ultrafast mid-infrared lasers. We have identified them as one major obstacle in the performance scaling potential of the aforementioned sources in general and first mitigation strategies have already been successfully applied.