It is generally agreed upon that power scaling in single-frequency continuous-wave (CW) fiber amplifiers is primarily impaired by the onset of stimulated Brillouin scattering (SBS). Consequently, several techniques have been implemented or suggested to suppress SBS in fiber amplifiers including large-mode area (LMA) fibers [1], thermal gradients [2], fibers possessing acoustic index of refraction gradients [3], and multitone amplification [4]. State-of-the-art conventional LMA fibers are generally limited in practice to diameters that are less than 30 urn. This makes photonic crystal fibers (PCFs) attractive as a means to mitigate the SBS process. The introduction of micron-sized air holes in the cladding allows for more precise control of the numerical aperture and thus leads to larger cores while maintaining single-mode operation.
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