Neodymium-doped silica single-mode fibre lasers

First results are presented on single-mode Nd(3+)-doped fiber lasers using low-loss fibers having small dopant concentrations. The low Nd(3+) content has made possible the construction of long laser devices in an end-pumped configuration, using both Fabry-Perot and ring-cavity resonators. The high-reflectivity F-P cavity has given a threshold as low as 100 micro-W of absorbed power from a GaAlAs diode laser pump; in this case, stable CW operation of a few microwatts output was observed at a wavelength of 1.088 micron. An all-fiber Nd-doped ring cavity laser was also constructed; when pumped with a dye laser at 595 nm, the output from one port was 2 mW for about 20 mW absorbed in the ring with a threshold of a few mW. These experiments confirm the potential of a wide range of active fiber devices based on low-level rare-earth doping in low-loss silica fibers.