Investigation of Nd:Yb - codoped silica fibers as a laser material
The increasing interest in high power fiber lasers is connected with the task of providing the necessary pump energy at acceptable costs. High power laser experiments with commercially available multi-wavelengths diode laser systems and silica fibers codoped with Neodymium (Nd) and Ytterbium (Yb) demonstrated the potential of this laser concept. Fluorescence investigations of Nd:Yb-codoped silica fibers proved an effective energy transfer from stimulated Nd ions to Yb ions. To get a better understanding of this laser medium we investigated the fluorescence spectra, the fluorescence decay and the laser characteristics both experimentally and theoretically. In conclusion, we present experimental results and a model for the understanding of fluorescence and laser properties of Nd:Yb-codoped silica fibers
Nd:Yb-codoped silica fibers for high power fiber lasers: fluorescence and laser properties
We have doped the core of Ytterbium (Yb) laser fibers additionally with Neodymium (Nd) to exploit wavelength-multiplexed high-power pump systems, which are commercially available. By pumping such a Nd:Yb-codoped fiber with the 808/940/978 nm-diode system, we could demonstrate CW output powers of more than 1 kW with high laser slope efficiency. In order to get a better understanding of this laser medium, we studied the fluorescence and the laser behavior of Nd:Yb fibers with different rare earth concentrations in comparison to a fiber doped solely with Nd. A theoretical model for the calculation of the fluorescence decay curve and spectrum as well as the laser characteristic and wavelength was developed, that takes the energy transfer process from Nd to Yb ions into account. Comparing the experimental and theoretical results, the behavior of the Nd:Yb high power fiber laser is understood as a collective emission of both ion types within the same wavelength region. These investigations contribute to the optimization of high power fiber lasers under the viewpoint of thermal load.
Mean field model of a game for power
Abstract Our aim is to model a game for power (equivalent to total energy) as a dynamical process, where an excess of power possessed by a player allows him to gain even more power. Such a positive feedback is often termed as the Matthew effect. Analytical and numerical methods allow to identify a set of stationary states, i.e. fixed points of the model dynamics. The positions of the unstable fixed points give an insight on the basins of attraction of the stable fixed points. The results are interpreted in terms of modeling of coercive power.