Kirill V. Zotov

Effect of the AlPO4 join on the pump-to-signal conversion efficiency in heavily Er-doped fibers.

Heavily Er-doped fibers (EDFs) based on P(2)O(5)-Al(2)O(3)-SiO(2) (PAS) ternary glass have been studied. A unique feature of this glass is the formation of a AlPO(4) join having a structure similar to that of SiO(2) glass and a refractive index below it. It is found that the Er(3+) absorption and emission spectra in the PAS EDFs are defined by the dopant (Al(2)O(3) or P(2)O(5)) present in excess and are close to those of the corresponding binary glass (Al(2)O(3)-SiO(2) or P(2)O(5)-SiO(2)). The presence of the AlPO(4) join results in the enhancement of the pump-to-signal conversion efficiency in the PAS EDFs as compared with the EDFs based on the P(2)O(5)-SiO(2) and Al(2)O(3)-SiO(2) (with 1.5 mol. %Al(2)O(3) and less) binary glasses. The PAS host glass is advantageous in the case of large-mode-area active fibers.

Radiation Resistant Er-Doped Fibers: Optimization of Pump Wavelength

H-free and H-loaded pieces of a carbon-coated erbium-doped fiber (EDF) are gamma-irradiated to doses in the range 0.1-10 kGy. In three months after the irradiation, optical loss spectra and lasing efficiency of the fibers are studied. It is found that the slope efficiency of a laser based on an irradiated EDF quickly grows under the action of pumping at the wavelength of 980 nm, owing to photobleaching of radiation-induced color centers. Photobleaching is found to be much more efficient in H2-loaded EDFs. No photobleaching occurs with pumping at 1480 nm. Pumping at 980 nm is argued to ensure a sufficiently long service life of H2-loaded EDFs in space, much longer than in the case of pumping at 1480 nm.

Radiation-Resistant Erbium-Doped Fiber for Spacecraft Applications

Radiation-induced absorption and lasing efficiency of a hermetically coated erbium-doped fiber saturated with molecular hydrogen are studied. It is shown that H2-loading of hermetically coated erbium-doped fibers prolongs their service time in space more than in 5 times, making such fibers promising for space applications.

Radiation Resistance of Er-Doped Silica Fibers: Effect of Host Glass Composition

With the aim to find the best-suited host glass for radiation-resistant erbium-doped fibers (EDF), radiation-induced absorption (RIA) is measured and analyzed after γ -irradiation to 3.0-4.5 kGy in 18 silica optical fibers with various concentrations of dopants: Al₂O₃ , P₂O₅ , GeO₂ and Er₂O₃ . The RIA dependence on the content of Al₂O₃, P₂O₅ and Er₂O₃ in singly doped fibers is investigated. RIA of fibers codoped simultaneously with Al₂O₃ and P₂O₅ are found to be significantly lower than those of singly Al₂O₃ -doped fibers. This is explained as the result of the formation of AlPO₄-joins in the silica network. GeO₂ codoping of AlPO₄ -doped silica is shown to further reduce RIA. Nevertheless, the application of H₂ -loading and photobleaching of RIA by 980-nm laser radiation shows that the AlPO₄ - and GeO₂ -codoped silica is outperformed by P-free Al₂O₃- and GeO₂-codoped silica, which is, therefore, concluded to be the best host glass composition for radiation resistant EDFs.

Fabrication of heavily Er2O3 doped aluminophosphosilicate glass fibers

This work examines vapor-phase doping of aluminophosphosilicate (APS) glasses with erbium oxide using Er(dpm)3 (erbium dipivaloylmethanate) as a metalorganic precursor. We describe two vapor-phase processes for Er2O3 doping of APS glasses for fiber cores. In one of them, a standard MCVD procedure, all the oxides of the glass core are deposited simultaneously. With this procedure, the erbium content of the APS glasses does not exceed 1 wt % because of the reaction of AlCl3 with POCl3 and Er(dpm)3. In the other procedure, a porous Al2O3-P2O5-SiO2 layer is infiltrated with Er2O3 from the vapor phase. Owing to the separation of the reactant flows, this procedure ensures considerably higher rare-earth doping levels in the APS glasses, up to several weight percent.

H 2 -Loaded Carbon-Coated Er-Doped Fibre with Enhanced Radiation Resistance

An H2-loaded hermetically carbon-coated Er-doped fibre is found to have a significantly lower optical loss after ¿-irradiation to 2.0 kGy than its H2-free analogue and is therefore argued to be a promising fibre design for space applications.