Mode instability thresholds for Tm-doped fiber amplifiers pumped at 790 nm

• Published in: Optics express Vol. 24; no. 2; pp. 975 - 992
• Main Authors: Smith, Arlee V, Smith, Jesse J
• Format: Journal Article
• Language: English
• Published: United States 25.01.2016
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.24.000975

We use a detailed numerical model of stimulated thermal Rayleigh scattering to compute mode instability thresholds in Tm(3+)-doped fiber amplifiers. The fiber amplifies 2040 nm light using a 790 nm pump. The cross-relaxation process is strong, permitting power efficiencies of 60%. The predicted instability thresholds are compared with those in similar Yb(3+)-doped fiber amplifiers with 976 nm pump and 1060 nm signal, and are found to be higher, even though the heat load is much higher in Tm-doped amplifiers. The higher threshold in the Tm-doped fiber is attributed to its longer signal wavelength, and to stronger gain saturation, due in part to cross-relaxation heating.