1.1 μm Femtosecond Laser Pulses Generation From 1.06 μm Self-Seeded Picosecond Coherent Raman Fiber Amplification and Frequency Shift

Although the Raman fiber amplifiers are attractive for their unique advantages and various Raman fiber amplifiers in continuous wave (CW) regime were built, there are a few fundamental limitations for short-pulsed Raman fiber amplifiers. In this paper, we present a theoretical and experimental study on a novel method termed picosecond (ps) coherent Raman fiber amplification, where the stimulated Raman scattering is employed to generate high-quality femtosecond pulses from narrowband ps pump pulses, with high conversion efficiency and compact construction. Detailed numerical simulation reveals the nonlinear dynamics of the ps-coherent Raman fiber amplification in an Yb-doped gain fiber. The spectral filtering effect induced by finite Raman gain bandwidth significantly improves the temporal quality of the generated Raman pulses, similar to the well-known Mamyshev regenerator. By employing this method in a 4.5 m Yb-doped polarization maintaining double-clad fiber, 67 nJ, 76 fs nearly transmission limited Raman pulses are generated from narrowband (<;2 nm) ps pump pulses, which have obvious pedestal. The corresponding peak power is close to 1 MW and the conversion efficiency reaches ~30%. Simulations also indicate that this method can be trivially adapted to other passive fibers with normal group-velocity dispersion. This simple and compact scheme, which combines the Raman fiber amplifier and Mamyshev regenerator, could be attractive for applications in ultrafast science and technology.