PROPERTIES AND FABRICATION OF YTTERBIUM-ERBIUM CO-DOPED SILICA FIBERSFOR HIGH-POWER FIBER LASERS

The fabrication, properties and performance of ytterbium-erbium co-dop ed silica optical fibres for high-power lasers generating ultra-short pulses at 1.55 mu m when pumped at 1.064 mu m are described. The fibre cores composed of Al2O3-P2O5-SiO2 glass immobilizing the rare-earth i ons are prepared by the modified solution-doping method. Improved sint ering conditions have allowed us to increase the P2O5 concentration to about Is mol % and to prevent the depletion of this dopant in the cen tral part of the core. The prepared fibres have been tested in an expe rimental ring laser. A maximum power conversion efficiency of 24% and intra-cavity signal powers of about 600 mW at 1.59 mu m have been meas ured 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 f ibres. In the conditions of active mode-locking, a stable 4 GHz train of 2 ps solitons with an avenge power of 130 mW has been generated wit h this laser.