Single-mode Er/Yb fiber MOPA at 1562nm with 302W power and 56% optical efficiency

We have demonstrated a new record of 302W single-mode power from an Er/Yb co-doped fiber master oscillator power amplifier (MOPA) with a record optical efficiency of 56%. This single-mode power is a new record for any lasers in this wavelength range. The previous record of single-mode power from an Er/Yb fiber laser pumped by a 9xx nm diode was 207 W at 1560 nm. The new optical efficiency of 56%, very close to the quantum-limited efficiency of 58.6%, is also a new record for Er/Yb fiber lasers. This new result is made possible mainly due to new fiber development from Nufern and off-resonant pumping of the Er/Yb fiber, which demonstrates further power-scaling potentials of Er/Yb fiber lasers pumped by widely available 9xx nm diodes. We also show that further power scaling is no longer limited by Yb3+ parasitic lasing near 1.06 mu m, but by fiber fuse in the Er/Yb fiber. The Yb3+ amplified spontaneous emission (ASE) was found to be negligible in all the cases we tested. Nonetheless, our numerical investigation shows that off-resonance pumping at 915 nm or 940 nm only plays a small role in the above-mentioned negligible ASE. We believe that the major cause may be the high Er3+ doping level in the Nufern Er/Yb co-doped fiber. Our results provide significant new insights and will stimulate further power scaling of Er/Yb fiber lasers and amplifiers.