Researchers at Imperial College in London have produced 3.8 W of continuous-wave light with a bandwidth exceeding 1000 nm by pumping holey fibers with a 10-W, single-mode, seeded ytterbium fiber amplifier.As they report in the Sept. 16 issue of Applied Physics Letters, low-loss coupling of holey fibers to standard, single-mode fibers could enable the setup to be developed into a fully fiber-integrated, multiwatt-average-power, white light source.