High power, narrow linewidth fiber lasers

Abstract

Single transverse mode fiber lasers have recently achieved output powers at the kilowatt level. These breakthroughs can be attributed to the maturation of high power diode pump technology at 980 nm and the use of large mode area (LMA) fibers. In the continous wave (cw) operation regime, LMA fibers, through their reduction of device length and increase of the effective area, have been effective in the reduction of deleterious nonlinear optical effects such as stimulated Raman scattering (SRS). The use of LMA fiber has been less effective in the suppression of stimulated Brillouin scattering (SBS), for which the threshold can be several orders of magnitude lower than for SRS. In this work we use refractive index profiles and index modifying dopant distributions for the mitigation of SBS. Our theoretical and modeling efforts led to an experimentally demonstrated increase in SBS threshold of 2.5 dB for single mode fiber and 6 dB for LMA amplifier fiber. We discuss the use of this SBS-suppressive fiber in the demonstration of a high-power, narrow linewidth fiber amplifier.