A compact upconversion fiber laser operating around 810 nm is proposed using thulium-doped silica-based fiber with locally modified thulium environment by high alumina codoping. Using a comprehensive numerical model of thulium doped fiber we investigate performance of the proposed laser. Comparison with two other thulium hosts, fluoride glass and standard silica, is presented. Efficient lasing can be expected even for silica based fiber for specific ranges of the fiber and laser cavity parameters, especially when ³H₄ lifetime is enhanced. With moderate pump power of 5 W at wavelength of 1064 nm, the predicted output power of the upconversion laser is about 2 W at 810 nm.

In this Letter, we demonstrate a graphene mode-locked, all-fiber Ho-doped fiber laser generating 1.3 nJ energy pulses directly from the oscillator. The graphene used as a saturable absorber was obtained via chemical vapor deposition on copper substrate and immersed in a poly(methyl methacrylate) support. The laser generated ultrashort soliton pulses at 2080 nm with bandwidth up to 6.1 nm. The influence of the output coupling ratio and the SA modulation depth on the mode-locking performance was also investigated.

Self-sweeping of laser wavelength corresponding to holmium emission near 2100 nm is reported. The sweeping occurred in ~4 nm interval with rate ~0.7 nm/s from longer towards shorter wavelengths. Origins of the selection of the sweeping direction are discussed. The laser wavelength drift with time was registered by Fourier transform infrared spectrometer. To our knowledge it is the first observation of self-swept fiber laser beyond 2000 nm.

The spectroscopic properties of Tm³⁺/Yb³⁺ co-doped silica fibers under excitation at 980 nm are reported. Three distinct up-conversion fluorescence bands were observed in the visible to near infra-red regions. The blue and red fluorescence bands at 475 and 650 nm, respectively, were found to originate from the ¹G₄ level of Tm³⁺. A three step up-conversion process was established as the populating mechanism for these fluorescence bands. The fluorescence band at 800 nm was found to originate from two possible transitions in Tm³⁺; one being the transition from the ³H₄ to ³H₆ manifold which was found to dominate at low pump powers; the other being the transition from the ¹G₄ to ³H₆ level which dominates at higher pump powers. The fluorescence lifetime of the ³H₄ and ³F₄ levels of Tm³⁺ and ²F_5/2 level of Yb³⁺ were studied as a function of Yb³⁺ concentration, with no significant energy back transfer from Tm³⁺ to Yb³⁺ observed.

We present a review on recent progress in the research and development of nanoparticlecontaining optical fibers for high-power fiber lasers, amplifiers, and ASE sources. Attention has been focused on rare-earth-doped silica fibers with nanoparticles in the core. Progress in materials, technologies, characterization techniques, and achievements has been summarized. Materials of active fibers based on yttrium-aluminium silicates, mullite, protoenstatite, and phosphates doped with Er³⁺, Yb ³⁺, Eu³⁺, and Tm³⁺ have been reviewed. The material research in this field has been systematically investigated by research groups from ORC Southampton, CGCRI Kolkata, LPMC Nice together with CNR-IOM-OGG Grenoble, nLIGHT (formerly Liekki), and IPE Prague since 2007. The best slope efficiency achieved with Yb –doped nanoparticle-containing fiber was in the range of 70-80 %.