Abstract

The utility of Raman spectroscopy as a means of characterizing the properties of pure and doped fused silica has been investigated. Laser-Raman spectra were obtained by forward scattering from solid optical fibers ~35 to 85 m in length using 514.5 nm excitation with an "image slicer" and a Cary model 81 instrument. Clad and unclad fibers of fused silica and doped fibers having SiO₂-GeO₂ and SiO₂-GeO₂-B₂O₂ cores were examined. Raman spectra were also obtained from bulk samples of glasses, including pure GeO₂, pure B₂O₃, and various compositions of SiO₂-GeO₂, SiO₂-B₂O₃, and SiO₂-GeO₂-B₂O₃. The addition of dopants to fused silica was found to alter the Raman spectrum both by the appearance of new bands, roughly proportional to dopant concentration and not common either to the fused silica or to the dopant alone, and by the marked alteration of other Raman bands, which is indicative of changes in the local intermolecular order. Thus, addition of GeO₂ produces new Raman bands at ~675 and ~1000 cm⁻¹; and of B₂O₃, new bands at ~940 and ~1350 cm⁻¹. Addition of GeO₂ and/or B₂O₃ weakens the relatively sharp Raman lines near 485 and 600 cm⁻¹ (and a similar but small effect was also noted with increasing OH content). GeO₂ and B₂O₃ together also produce observable narrowing of the broad intense 440 cm⁻¹ Raman contour. These spectral effects are interpreted, respectively, in terms of a decrease in the concentrations of [Equation] and [Equation] defects produced by dopant addition and of a concomitant reordering of the silica structure. Raman spectroscopy thus appears to be a useful optical technique for elucidating the properties of dopants that have been especially chosen for good optical transmission and hence are not easily detectable by absorption measurements.

Experimental measurements of the spectral absorption coefficient of pure fused silica optical fibers

Travis J. Moore and Matthew R. Jones
Appl. Opt. 54(6) 1374-1378 (2015)

Optical spectroscopy of bismuth-doped pure silica fiber preform

I. Razdobreev, H. El Hamzaoui, V. Yu. Ivanov, E. F. Kustov, B. Capoen, and M. Bouazaoui
Opt. Lett. 35(9) 1341-1343 (2010)

Fused silica as an optical material [Invited]

Lisa A. Moore and Charlene M. Smith
Opt. Mater. Express 12(8) 3043-3059 (2022)

1.2W laser amplification at 1427nm on the ⁴F_3/2 to ⁴I_13/2 spectral line in an Nd³⁺ doped fused silica optical fiber

Jay W. Dawson, Paul H. Pax, Graham S. Allen, Derrek R. Drachenberg, Victor V. Khitrov, Nick Schenkel, and Michael J. Messerly
Opt. Express 24(25) 29138-29152 (2016)

Bismuth-doped hafnia-yttria-alumina-silica based fiber: spectral characterization in NIR to mid-IR

A. V. Kir’yanov, S. H. Siddiki, Y. O. Barmenkov, D. Dutta, A. Dhar, S. Das, and M. C. Paul
Opt. Mater. Express 7(10) 3548-3560 (2017)