SBS Threshold Dependence on Pulse Duration in a 2053 nm Single-Mode Fiber Amplifier

Stimulated Brillouin scattering (SBS) is the first nonlinear effect that limits power scaling of narrow linewidth fiber lasers. Nonlinearities typically have a reduced impact when operating at longer wavelengths. However, the SBS gain is considered wavelength independent. To investigate this further, a pulsed 2053 nm source with MHz-linewidth is amplified to >100 W peak powers in single-mode, thulium-doped fiber. The SBS thresholds were measured while varying the pulse duration. Analyzing the SBS threshold measurements suggests that the peak Brillouin gain coefficient is ~12.2 pm/W with a spontaneous Brillouin bandwidth of ~17.5 MHz in the passive single-mode fiber at 2053 nm. While the peak Brillouin gain coefficient is comparable to those reported at shorter wavelengths, the spontaneous Brillouin bandwidth is significantly narrower. This indicates that long wavelength sources can inhibit the onset of SBS more readily than short wavelength sources.