Nanometer-scale heterogeneity in SiO2-GeO2 glass preforms and fibers prepared by vapor phase axial deposition method

Nanometer-scale heterogeneity of Ge ions in SiO2:GeO2 (10-15 mol %) glass preforms prepared by vapor phase axial deposition method and in optical fibers drawn from the preform was found by transmission electron microscopic observation. Both preforms and fibers were comprised of 8-10 nm sized Ge-rich and Si-rich phases. Observation of Ge E' centers in the as-prepared state and the formation of Ge E' centers with light illumination with 5 eV-light may be understood by the occurrence of these heterogeneity. (C) 1996 American Institute of Physics.