Abstract
We numerically simulate and optimize a high-power fiber Raman amplifier cladding pumped by spectrally combined diode lasers at wavelengths from ∼0.9 to ∼1 μm in the continuous-wave regime. This amplified a signal at the first-Stokes wavelength of 1024 nm. We found that it was possible to add pumps over an increasingly wide wavelength span up to ∼90 nm, while still maintaining an incremental conversion efficiency higher than 60%, even though the Raman linewidth is only ∼15 nm. We investigated the dependence on the power of individual diode lasers and on the wavelength spacing and found that the total conversion efficiency reaches ∼70 % with realistic pump sources based on state-of-the-art diode lasers. We believe this study shows the potential for high-power fiber Raman lasers pumped by spectrally combined multiwavelength diode and fiber laser sources.
Highlights
Stimulated Raman scattering (SRS) can be an efficient process for generation and amplification of light in optical fibers
We present simulation results of multiwavelength cladding-pumping in the 0.9- 1-μm wavelength range of a high-power fiber Raman amplifier (FRA) in the continuous-wave regime, with fixed and optimized pump wavelength spacings of 5 to 30 nm
We have used numerical simulations to investigate multiwavelength cladding-pumping directly with diode lasers of high-power FRAs operating on the first Stokes wavelength of the longest-wavelength pump
Summary
Stimulated Raman scattering (SRS) can be an efficient process for generation and amplification of light in optical fibers. The pump acceptance bandwidth of SRS in high-silica fibers is limited to the Raman linewidth of ∼5 THz (∼15 nm at 1 μm) in the conventional case of the first-order Raman conversion with high Raman gain coefficient gR, i.e., when the pump wavelength is separated from the Stokes wavelength by approximately the peak Raman shift νpeak. Our work confirms the potential for multiwavelength diode-laser off-resonance pumping with total pump bandwidth significantly larger than the Raman linewidth for further power scaling and improved efficiency of diode-laser-pumped fiber Raman sources. This applies to important multi-kW spectrally combined diode-laser sources in rapid development for direct-diode materials processing
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