High power tandem pumping fibre amplifier

We demonstrate a high efficiency 1083 nm fibre amplifier tandem pumped by a 1030 nm fibre laser. The 1030 nm fibre laser is coupled into a 25 m long single clad ytterbium doped fibre via a high power wave division multiplexer to core pump the 1083 nm signal laser. An output power of 4.5 W and a power conversion efficiency of 76.6% are achieved without power-roll. The performance of the amplifier can be improved by optimizing the gain fibre length.