High-energy, in-band pumped erbium doped fiber amplifiers

We have demonstrated and compared high-energy, in-band pumped erbium doped fiber amplifiers operating at 1562.5 nm under both a core pumping scheme (CRS) and a cladding pumping scheme (CLS). The CRS/CLS sources generated smooth, single-peak pulses with maximum pulse energies of similar to 1.53/1.50 mJ, and corresponding pulse widths of similar to 176/182 ns respectively, with an M-2 of similar to 1.6 in both cases. However, the conversion efficiency for the CLS was >1.5 times higher than the equivalent CRS variant operating at the same pulse energy due to the lower pump intensity in the CLS that mitigates the detrimental effects of ion concentration quenching. With a longer fiber length in a CLS implementation a pulse energy of similar to 2.6 mJ is demonstrated with a corresponding M-2 of similar to 4.2. Using numerical simulations we explain that the saturation of pulse energy observed in our experiments is due to saturation of the pump absorption. (C)2012 Optical Society of America