17 March 2014 Stimulated Brillouin scattering suppression with a chirped laser seed: comparison of dynamical model to experimental data
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Abstract
When scaling CW single-mode fiber amplifiers to high power, the first nonlinear limitation that appears for narrowlinewidth seed lasers is stimulated Brillouin scattering (SBS). We present a dynamical simulation of Brillouin scattering in a Yb-doped fiber amplifier that numerically solves the differential equations in z and t describing the laser, Stokes and pump waves, the inversion, and the density fluctuations that seed the scattering process. We compare the model to experimental data, and show that a linearly chirped seed laser is an efficient form of SBS suppression; especially for long delivery fibers. The frequency chirp decreases the interaction length by chirping through the Brillouin resonance in a time that is short compared to the fiber transit time. The seed has a highly linear chirp of 1014 – 1016 Hz/s at 1064 nm which preserves a well-defined phase relationship in time. This method of SBS suppression retains a long effective coherence length for purposes of coherent combining, while at high chirps appears to the SBS as a large linewidth, increasing the threshold. An increase in fiber length increases the laser bandwidth as seen by the SBS, leading to a fiberlength- independent SBS threshold.
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Eliot Petersen, Zhi Yang, Jeffrey O. White, George Rakuljic, Naresh Satyan, Arseny Vasilyev, Amnon Yariv, "Stimulated Brillouin scattering suppression with a chirped laser seed: comparison of dynamical model to experimental data", Proc. SPIE 8961, Fiber Lasers XI: Technology, Systems, and Applications, 89613H (17 March 2014); doi: 10.1117/12.2037750; https://doi.org/10.1117/12.2037750
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