High-energy single-transverse-mode Q-switched fiber laser based on a multimode large-mode-area erbium-doped fiber

We demonstrate that appropriately designed doped multimode fibers provide robust single-mode output when used within a fiber laser cavity. Using a novel large-mode-area fiber, we demonstrate what we believe to be record single-mode (M-2 < 1.2) pulse energies of >0.5 mJ from a Q-switched fiber laser and even higher pulse energies las high as 0.85 mJ) with slightly compromised spatial-mode quality (M-2 < 2.0). This approach offers significant scope for extending the range of single-mode output powers and energies that are achievable from fiber-laser-amplifier systems. (C) 1998 Optical Society of America.