Diffusion of phosphorus doped silica for active optical fibers

Kirchhof, J.; Unger, Sonja; Dellith, Jan

doi:10.1016/j.jnoncrysol.2004.08.028

Cited by 11 publications

(9 citation statements)

References 13 publications

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“…Diffusivities of both Al and P in silica are strong functions of concentration 88–90 . Between 0 and 10 mol% P 2 O 5 , the P diffusion coefficient (extrapolated to 1200°C) increases by nearly four orders of magnitude 88 .…”

Section: Discussionmentioning

confidence: 99%

“…Thus, P from the monazite coatings on top of the growing SiO 2 layer 7,12 and Al from the fiber/SiO 2 interface can be expected to diffuse toward each other due to the gradient of chemical potential. As the diffusion coefficient of Al in silica glass at 1200°C is nearly an order of magnitude higher than that of P 66,88–90 (Table IV), Al should diffuse outward and segregate in an Al/P‐rich layer on top of the oxide scale. As discussed above, even a fraction of a monolayer of aluminum on a silicon surface can retard oxidation 84–86 .…”

Section: Discussionmentioning

confidence: 99%

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Monazite Coatings on SiC Fibers II: Oxidation Protection

Mogilevsky¹,

Boakye²,

Hay³

et al. 2006

Journal of the American Ceramic Society

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The effect of monazite on the oxidation of SiC was studied in laboratory and dry air. Monazite inhibited the oxidation of Tyranno‐SA™, Tyranno‐ZX™, Sylramic, and Hi‐Nicalon SiC fibers. Oxidation of pure chemical vapor deposition SiC and undoped SiC single crystals was not inhibited by monazite. Dry oxidation of both uncoated and monazite‐coated Tyranno‐SA™ fibers initially displayed parabolic kinetics with an activation energy of 180–190 kJ/mol. Subsequently, the oxidation rate of monazite‐coated fibers increased and the oxide‐scale growth rate approached that of the uncoated fibers. No differences in the composition or structure of the silica oxidation product could be detected between uncoated and coated fibers using transmission electron microscopy and energy‐dispersive spectroscopy. Possible mechanisms of the inhibition of SiC oxidation by monazite are discussed.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Monazite Coatings on SiC Fibers II: Oxidation Protection

Mogilevsky¹,

Boakye²,

Hay³

et al. 2006

Journal of the American Ceramic Society

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“…Dopant diffusion has been evaluated during MCVD processing of silica preforms with various dopants [5,6,8,13]. The basic concepts developed there will be applied to the fiber drawing process.…”

Section: Thermodynamical Kinetic and Geometrical Approximationsmentioning

confidence: 99%

“…While in case of stacks of undoped silica rods the simultaneous sintering and stretching faces no problems in terms of bubble formation or geometrical deformation, the use of doped silica rods or canes induces structural defects by gas phase reactions during thermal processing. A few papers [5,6,7,8,9] studied the diffusion of fluorine, germanium and other dopants during preparation of doped silica preforms and fiber drawing. High temperature and long process time cause flattening or broadening of dopant profiles.…”

Section: Introductionmentioning

confidence: 99%

Diffusion and Interface Effects during Preparation of All-Solid Microstructured Fibers

Kobelke¹,

Jörg²,

Wondraczek³

et al. 2014

Materials

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All-solid microstructured optical fibers (MOF) allow the realization of very flexible optical waveguide designs. They are prepared by stacking of doped silica rods or canes in complex arrangements. Typical dopants in silica matrices are germanium and phosphorus to increase the refractive index (RI), or boron and fluorine to decrease the RI. However, the direct interface contact of stacking elements often causes interrelated chemical reactions or evaporation during thermal processing. The obtained fiber structures after the final drawing step thus tend to deviate from the targeted structure risking degrading their favored optical functionality. Dopant profiles and design parameters (e.g., the RI homogeneity of the cladding) are controlled by the combination of diffusion and equilibrium conditions of evaporation reactions. We show simulation results of diffusion and thermal dissociation in germanium and fluorine doped silica rod arrangements according to the monitored geometrical disturbances in stretched canes or drawn fibers. The paper indicates geometrical limits of dopant structures in sub-µm-level depending on the dopant concentration and the thermal conditions during the drawing process. The presented results thus enable an optimized planning of the preform parameters avoiding unwanted alterations in dopant concentration profiles or in design parameters encountered during the drawing process.

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“…Recently, diffusion coefficients in the system cP 2 O 5 @ (100-c)@SiO 2 have been determined at temperatures between 1700°C and 2000°C and in a concentration range c between 0 and 10 mol% P 2 O 5 [12]. Our modeling is grounded on these data, however, we will extrapolate the values of diffusion coefficients beyond the experimentally covered region concerning both temperature and concentration which seems not unreasonable because the results of [12] could be well described by a close formula …”

Section: Modeling Of Phosphorus Diffusion During Mcvd Deposition and mentioning

confidence: 99%

Spatial distribution effects and laser efficiency in Er/Yb-doped fibers

et al. 2004

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It is well known that the efficiency of silica based Er/Yb fiber lasers and amplifiers can be greatly enhanced by a high level of phosphorus co-doping. The interaction of phosphorus with the rare earths and with the further co-dopant aluminium during the preparation process leads to peculiar effects concerning chemistry of dopant incorporation, diffusion behaviour and microscopic glass structure. Until now however, it has been disregarded that these interactions give rise to strong radial and even axial concentration profiles in preform and fiber (for the codopants phosphorus and aluminium, but also for the rare earth components erbium and ytterbium) with remarkable consequences for the laser efficiency. Here, we have studied the incorporation mechanism and the diffusion behaviour (diffusion coefficients in dependence on temperature and concentrations) by X-ray microprobe analysis concerning the dopant interaction effects. Moreover, we have investigated both fluorescence intensities and lifetimes, radially and axially resolved in the fiber preforms. The results were correlated with the properties of double clad fiber lasers made from these preforms. First attempts have been undertaken to interpret and control the incorporation mechanism on the basis of model calculations regarding phosphorus diffusion and chemistry.

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Diffusion of phosphorus doped silica for active optical fibers

Cited by 11 publications

References 13 publications

Monazite Coatings on SiC Fibers II: Oxidation Protection

Monazite Coatings on SiC Fibers II: Oxidation Protection

Diffusion and Interface Effects during Preparation of All-Solid Microstructured Fibers

Spatial distribution effects and laser efficiency in Er/Yb-doped fibers

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