We report up-conversion in a fluorozirconate Tm3+-doped fiber pumped by the first and second Stokes components of a Raman-shifted Nd3+:YAG laser. Relative fluorescence in the ultraviolet, blue, red, and near-infrared regions is analyzed as a function of the intensity ratio between the Stokes components. It is demonstrated that side fluorescence in the blue at 480 nm strongly dominates over other transitions when pumping with the two Stokes components. This suggests that high-efficiency blue up-conversion lasing is possible by using this pumping scheme with double-clad, Nd3+- or Yb3+-doped fiber laser pumps.

We report a single-mode, highly stable, continuous-wave Ho³⁺: ZBLAN fiber laser. The system was pumped by a 1175-nm fiber Raman laser and emitted at ∼2950 nm. The optical-to-optical conversion efficiency was 43% that is the highest reported in the literature. Characterizations revealed a quasigaussian intensity profile with a power stability of less than 1%. This high stability relies on the single-wavelength emission of the system because the system does not require simultaneous oscillation at 2100 nm. Coincidence between the emission wavelength and the absorption peak of water makes the system suitable to replace a high-power (∼9.34-W) Er³⁺: ZBLAN fiber laser for cutting materials with high moisture content.

We report here the efficiency improvement in a fiber Raman laser by splicing to it short pieces of 10000-ppm Yb³⁺-doped fibers. The amplified spontaneous emission produced by the doped fiber started the stimulated Raman scattering earlier than the spontaneous scattering in the 350-m silica-fiber cavity. In the best case, when splicing to the cavity 127 cm of doped fiber, the pump threshold decreased from 2.9 down to 1.27 W, representing a 56% improvement. This power was close to the theoretical minimum of 1.25 W for very long fibers. The second stokes signal (1175 nm) was only present when the doped fibers were inserted. At 4-W pump, the non-doped cavity delivered 2 W of first stokes signal (1117 nm) that represent a 50% efficiency compared to ∼3 W delivered (∼75%) when a 34-cm doped fiber was inserted. This improvement is intended to reduce the cost of fiber Raman lasers because less powerful sources or shorter fibers are necessary to produce more stokes components.