8.74 kW (8+1) GT-wave fiber amplifier

A new-type of (8+1) GT-wave fiber was fabricated by our newly-optimized specialty fiber assembly and coating techniques for the first time. This (8+1) GT-wave fiber allowed for 10.66 kW aggregated pump power at 976 nm from 6 counter-pump-ports in a master oscillator power amplifier (MOPA) laser setup and stably presented 8.72 kW laser output at 1 079.4 nm with a high optical-to-optical efficiency of 81.0%. This is the highest power of the fiber amplifiers pumped by commercial laser diodes that has been reported so far, and only limited by the available pump power. Up to this power level, pure output spectrum with narrow 3 dB bandwidth Δλ_{3 dB} of 2.76 nm and without any sign of stimulated Raman scattering and amplified spontaneous emission was obtained. With other ten pump-ports to collect more pump power, a further power scaling towards 10 kW or above can be expected.