Stimulated Brillouin scattering suppression in optical fibers by hydrogen-loading technique

Abstract

Further power scaling of single frequency fiber lasers is of significant interests for many scientific and defense applications. It is currently limited by stimulated Brillouin scattering (SBS). In recent years, a variety of techniques have been investigated for the suppression of SBS in optical fibers. A notable example is to design transverse acoustic properties of optical fibers in order to minimize optical and acoustic mode overlap. It was pointed out recently that SBS suppression from such transverse acoustic tailoring is limited when considering the existence of acoustic leaky modes. We demonstrate, for the first time, a post-processing technique where hydrogen is diffused in to a fiber core and then locally and permanently bonded to core glass by a subsequent UV exposure. Large local acoustic property can be altered this way for significant SBS suppression. It is also possible to use this technique to implement precisely tailored acoustic properties along a fiber for more optimized SBS suppression in a fiber amplifier. Change in Brillouin Stokes frequency of ~320MHz at 1.064μm has been demonstrated using hydrogen, corresponding to a SBS suppression of ~8dB. Much higher SBS suppression is possible at higher hydrogen concentrations.