A novel method of increasing the efficiency of 1064 nm two tone amplifiers through heating of the gain fiber

The efficiency of two tone fiber amplifiers can be changed rather significantly by altering the temperature of the external environment surrounding the gain fiber. It is shown experimentally that changes in the temperature of the core of the gain fiber has dramatic effects on the 1064 nm / 1040 nm power distribution in the output of narrow linewidth 1064 nm two tone amplifiers with a greater percentage of the output being 1064 nm at higher core temperatures. By increasing the environmental temperature of the gain fiber from 20 to 80°C, the efficiency of a 1064 nm two tone amplifier can be increased up to 40% with the greatest increases seen in amplifiers seeded hardest in 1040 nm, i.e., having the smallest 1064 nm / 1040 nm seed ratios. This has been attributed to temperature dependence of the absorption and emission cross-sections at the wavelengths of interest. Finally, the temperature of the gain fiber can be used as a design tool to enable a higher efficiency 1064 nm two tone amplifier.