Raman Fiber Lasers and Amplifiers based on Multimode Fibers and their Applications to Beam Cleanup
Date of Award
Doctor of Philosophy (PhD)
Department of Engineering Physics
Thomas G. Alley, PhD
Raman fiber lasers (RFLs) and Raman fiber amplifiers (RFAs) in multimode fibers were explored. The RFL based on a graded-index fiber was shown to be very efficient relative to RFLs based on singlemode fibers. Several configurations of the RFL were examined; the beam quality of the Stokes beam depended on the reflectivity of the output coupler and the Stokes power. When used as a beam combiner, the RFL was a highly efficient brightness converter. RFL configurations which used dichroic mirrors were shown to be potentially useful for RFLs based on very large fibers. The forward- and backward-seeded geometries of an RFA based on a graded-index fiber were examined. The beam quality of the output was observed to depend on the beam quality of the input. A numerical model explains this behavior in terms of mode competition and explains why beam cleanup occurs in graded-index fibers but not in step-index fibers. The spectrum of the forward-seeded geometry was superior to the spectrum of the backward-seeded geometry. The RFA was used as a beam combiner.
DTIC Accession Number
Terry, Nathan B., "Raman Fiber Lasers and Amplifiers based on Multimode Fibers and their Applications to Beam Cleanup" (2007). Theses and Dissertations. 2896.