Effect of H-2/O-2 ratio on the GeO2 concentration profile in SiO2 : GeO2 glass preforms prepared by vapor-phase axial deposition

GeO2 radial concentration in silica glass preforms, prepared by vapor-phase axial deposition (VAD) method, was analyzed by X-ray fluorescence (XRF) me asurements. The results were used to evaluate the effect of the H-2/O-2 rat io used during the deposition process in the formation of the GeO2 concentr ation profile. Considering four different H-2/O-2 ratios, GeO2 distribution was observed to decrease monotonically with the increasing radius for H-2/ O-2 less than or equal to 1.5, and the acute shape around the core center o f the GeO2 concentration profile, decreased with increasing H-2/O-2 ratio. When the ratio H-2/O-2 = 2.5, the central doping of GeO2 was minimal, and a constant distribution was obtained along glass preform radii. The results seem to indicate that the control of spatial distribution in the concentrat ion of GeO2 deposited is favorable for the ratio H-2/O-2 less than or equal to 1.5. (C) 2000 Elsevier Science B.V. All rights reserved.