Properties and fabrication of ytterbium-erbium co-doped silica fibres for high-power fibre lasers

The fabrication, properties and performance of ytterbium-erbium co-doped silica optical fibres for high-power lasers generating ultra-short pulses at when pumped at are described. The fibre cores composed of glass immobilizing the rare-earth ions are prepared by the modified solution-doping method. Improved sintering conditions have allowed us to increase the concentration to about 18 mol % and to prevent the depletion of this dopant in the central part of the core. The prepared fibres have been tested in an experimental ring laser. A maximum power conversion efficiency of 24% and intra-cavity signal powers of about 600 mW at have been measured for contradirectional pumping with a CW Nd:YAG laser. The results of these measurements are related to the fibre waveguiding properties and the concentration profiles of the rare-earth ions in the tested fibres. In the conditions of active mode-locking, a stable 4 GHz train of 2 ps solitons with an average power of 130 mW has been generated with this laser.