Cladding-pumped Er-doped (Yb-free) fibres with Al2O3-SiO2 core highly doped with fluorine

• Published in: Laser physics letters 2020-01, Vol.17 (1)
• Main Authors: Khudyakov, M M, Yashkov, M V, Lipatov, D S, Abramov, A N, Vechkanov, N N, Bubnov, M M, Bobkov, K K, Guryanov, A N, Likhachev, M E
• Format: Article
• Language: English
• Subjects: Er-doped fibre; fibre laser; stimulated Brillouin scattering
• ISSN: 1612-2011; 1612-202X
• DOI: 10.1088/1612-202X/ab5d24

Double-clad Er-doped fibers highly doped with aluminum (up to 3 mol.%) and fluorine (up to 1.5 wt.%) have been fabricated and studied. The fibers have a core numerical aperture of approximately 0.055, which allowed us to achieve a single-mode propagation regime for a fiber core diameter of 35 µm. The possibility of increasing the pump-to-signal conversion efficiency in the L-band using the developed double-clad Er-doped fibers was demonstrated. Utilization of the F-GeO2-Al2O3-SiO2-Er fiber together with a P2O5-Al2O3-SiO2-Er fiber was found to be promising for single-frequency amplifiers because the fibers have negligible overlap of the stimulated Brillouin scattering gain. This feature allowed us to build a cascaded double-clad Er-doped fiber amplifier (two Er-doped fibers of different types were spliced one by one) with a threshold of stimulated Brillouin scattering greater than that of an amplifier based on a single Er-doped fiber with the same net length and pump-to-signal conversion efficiency.