Highly Efficient Micro-Joule All-Fiber Ultrafast Raman Amplifier at 1120-nm

We report a high-efficiency, high-energy, all-fiber, polarization maintaining, ultrafast Raman amplifier. The Raman laser consists of a ps pump seed and two pump/Raman fiber amplifiers. The ultrafast Raman seed is generated via stimulated Raman scattering in the first pump/Raman amplifier and amplified in the second pump/Raman amplifier. Eventually, Raman pulses centered at 1120-nm with a average power of 93-W, a pulse energy of 2.56-
$\mu \text{J}$
, a pulse width of 19.2-ps are delivered. The conversion efficiency (the ratio of the Raman pulse energy to the total energy) is ~89.5%, comparable to the conversion efficiency achieved by Raman fiber lasers based on soliton self-frequency shift. This simple and compact scheme provides a pathway for the generation of high-power, high-energy all-fiber, ultrafast Raman pulses with high conversion efficiency at 1.1-
$\mu \text{m}$
.