Abstract
The optical transparency and refractive index were measured over a wide wavelength range from the UV into the infrared for five glasses of potential use for long-wavelength optical fibers. The glasses contain 30–50 mole % GeO2 with the addition of Bi2O3, Tl2O, PbO, and Sb2O3. Indices were measured with a computerized refractometer to an accuracy of ±3 × 10−5 and were fitted within this accuracy to a three-term Sellmeier formula. This formula was then used to obtain interpolated index values, the dispersion, Abbé number, wavelength for zero material dispersion λ0, and slope of material dispersion vs wavelength (dM/dλ) at λ0. The temperature coefficients of the refractive index were also measured over a wide wavelength range, and the glasses were characterized by density, thermal expansion, glass transition, and crystallization temperatures. Raman and Brillouin spectra were also recorded on one of these glasses and the latter used to determine the elastic constants. The refractive indices ranged from nD = 1.93948 to nD = 2.28553, with Abbé numbers between 22.7 and 10.5. Values of λ0 were in the range from 2.08 to 2.81 μm combined with −dM/dλ values from 54.8 to 85.0 psec/nm ⋅ km ⋅ μm, significantly lower than that of fused silica (101 psec/nm ⋅ km ⋅ μm). These glasses show promise for waveguide fibers for the 3−4-μm region if ultrahigh purity specimens can be prepared.
© 1982 Optical Society of America
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