Dynamics of stimulated Raman scattering in double-clad fiber pulse amplifiers

A systematic analysis on dynamics of stimulated Raman scattering (SRS) in highly pumped ytterbium-doped double-clad fiber amplifiers during amplification of nanosecond pulses at tens-of-kilohertz repetition rates is presented. Energy and waveform evolutions of signal and Raman pulses in the amplifiers under forward, backward and bidirectional pump are depicted respectively. In consideration of the SRS components and incurred energy loss at the amplifier output, the detrimental effects of SRS on signal amplification for three pumping methods are quantitatively compared and comprehensively illustrated upon different signal, fiber and pump conditions. To avoid the performance deterioration, some limitations are also discussed.