Thulium-doped optical fibers for fiber lasers operating at around 2 μm

The paper deals with spectral and lasing characteristics of thulium-doped optical fibers fabricated by means of two doping techniques, i.e. via a conventional solution-doping method and via a nanoparticle-doping method. The difference in fabrication was the application of a suspension of aluminum oxide nanoparticles of defined size instead of a conventional chloride-containing solution. Samples of thulium-doped silica fibers having nearly identical chemical composition and wave guiding properties were fabricated. The sample fabricated by means of the nanoparticle-doping method exhibited longer lifetime, reflecting other observations and the trend already observed with the fibers doped with erbium and aluminum nanoparticles. The fiber fabricated by means of the nanoparticle-doping method exhibited a lower lasing threshold (by »20%) and higher slope efficiency (by »5% rel.). All these observed differences are not extensive and deserve more in-depth research; they may imply a positive influence of the nanoparticle approach on properties of rare-earth-doped fibers for fiber lasers

Erbium and Al2O3 nanocrystals-doped silica optical fibers

Fibre lasers and inherently rare-earth-doped optical fibers nowadays pass through a new period of their progress aiming at high efficiency of systems and their high power. In this paper, we deal with the preparation of silica fibers doped with erbium and Al2O3 nanocrystals and the characterization of their optical properties. The fibers were prepared by the extended Modified Chemical Vapor Deposition (MCVD) method from starting chlorides or oxide nanopowders. Conventional as well as modified approaches led to a nanocrystalline mullite phase formation in the fiber cores in which erbium is dissolved. The proposed modified approach based on starting nanopowders led to improved geometry of preforms and fibers and consequently to the improvement of their background attenuation. Such nanocrystal -doped fibers can be used for ASE sources. Further improvement of fiber optical properties can be expected