Narrow linewidth fiber laser systems via Brillouin-tailored optical fiber

We present some of our results in the design and implementation of Brillouin-tailored fibers for narrow linewidth fiber lasers and systems. We consider both rare-earth-doped active and passive fibers, and both traditional and large mode area (LMA) fibers. We show that by properly tailoring the acoustic profile, > 10 dB of Stimulated Brillouin scattering (SBS) suppression can be implemented. Data from manufactured fibers demonstrating > 10 dB SBS reduction, relative to traditional fibers of equivalent mode size, will be presented. Fiber laser configurations utilizing these fibers will be briefly described. Using models developed in-house, we show that transform-limited peak powers > 10 kW can be achieved. Importantly, we also consider the passive fibers employed as pigtails, component fibers, power delivery fibers, etc. in these systems. SBS can become the leading power impairment in systems incorporating 'reasonable' lengths of passive fiber. For example, this might be a 1-meter passive fiber pigtail at the output end of a pump/signal fiber combiner in a counter-propagating configuration. The counter-propagating configuration offers a reduced effective fiber length reducing the effects of non-linearities such as SBS. We will also discuss the possibility of designs with reduced photodarkening.