Integrated short-length PM fiber amplifiers for large-scale beam combining

We report the development and performance of short-length (10-20 cm) polarization-maintaining (PM) highly Yb^3+-doped and Yb^3+/Er^3+ co-doped phosphate fiber amplifiers at the 1-μm and 1.55-μm bands. Using a 10 cm, 20 wt.% Yb^3+-doped phosphate fiber, we achieved > 1 W output power at 1030 nm with only 1.6 W of pump power and an input signal of just 1 mW. Similarly, with an integrated 20-cm 3 wt.%Er^3+/1wt.%Yb^3+ co-doped fiber amplifier, we obtained 400 mW output power at 1560 nm with an input signal of 3 mW. These integrated short-length PM phosphate fiber amplifiers provide excellent performance as pre-amplifiers for large-scale fiber arrays, supporting high-efficiency coherent beam combining, particularly for pulse lasers.