Abstract

Extending earlier reports with lightly doped Nd fiber lasers,¹ cw lasers have been made from singlespatial mode fibers doped with relatively high concentrations of neodymium and end pumped with GaAIAs laser diodes emitting at 0.8 m and a krypton-ion laser at 0.752 and 0.799 μm. The fibers were drawn from MCVD prepared silica glass preforms doped by vapor transported neodymium compounds. The e^-1 lifetimes for various concentrations of Nd₂O₃ were measured and are reported. The fiber lengths varied from 1 to 20 cm. The lowest threshold at 1.06 μm was 0.09 mw incident on the fiber core for 99% reflectors. For emission at 0.905 μm from a 0.5-wt. % Nd₂O₃, 5-cm fiber, the threshold was 4.3 mW for reflectivities of 15, 94, and 20% at 0.8, 0.905, and 1.06 μm. At 1.4 μm, threshold was 6 mW for reflectivities of 10 and 99% at 1.06 and 1.4 μm. At 1.06 μm the linewidth at threshold was a few angstroms and broadened to over 5 nm, well above threshold. Replacing the exit end reflector with an etalon of two 50% reflectors separated by 5–50 μm gave a few angstroms linewidth tunable over 15 nm. At 1.06-μm oscillator temporal behavior, the singlepass amplifier, and its use as a superradiant source is described.

© 1986 Optical Society of America