2020, Trautvetter, Tom, Schäfer, Jan, Benzine, Omar, Methling, Ralf, Baierl, Hardy, Reichel, Volker, Dellith, Jan, Köpp, Daniel, Hempel, Frank, Stankov, Marjan, Baeva, Margarita, Foest, Rüdiger, Wondraczek, Lothar, Wondraczek, Katrin, Bartelt, Hartmut

An innovative approach using the vapor axial deposition (VAD), for the preparation of silica-based high-power fiber laser preforms, is described in this study. The VAD uses a plasma deposition system operating at atmospheric pressure, fed by a single, chemically adapted solution containing precursors of laser-active dopants (e.g., Yb2O3), glass-modifier species (e.g., Al2O3), and the silica matrix. The approach enables simultaneous doping with multiple optically active species and overcomes some of the current technological limitations encountered with well-established fiber preform technologies in terms of dopant distribution, doping levels, and achievable active core diameter. The deposition of co-doped silica with outstanding homogeneity is proven by Raman spectroscopy and electron probe microanalysis. Yb2O3 concentrations are realized up to 0.3 mol% in SiO2, with simultaneous doping of 3 mol% of Al2O3.

2021, Baeva, Margarita, Methling, Ralf, Uhrlandt, Dirk

A previously developed unified model of a tungsten-inert gas (TIG) microarc has been extended to take into account the melting of the anode made of copper and the release of copper atoms due to its evaporation. The copper atoms enter the plasma to become excited and ionized. The presence of copper atoms and ions can strongly change the plasma parameters. The extended unified model further includes excited states of copper and collisional and radiative processes between them. Predictions of the parameters of the microarc plasma in the presence of copper species are presented and discussed.