Optical properties of new oxide glasses with potential for long-wavelength optical fibers

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 % Ge0(2) with the addition of Bi(2)O(3), Tl(2)O, PbO, and Sb(2)O(3). Indices were measured with a computerized refractometer to an accuracy of +/-3 x 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, wave-length for zero material dispersion lambda(0), and slope of material dispersion vs wavelength (dM/dlambda) at lambda(0) 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 n(D) = 1.93948 to n(D) = 2.28553, with Abbé numbers between 22.7 and 10.5. Values of lambda(0) were in the range from 2.08 to 2.81 microm combined with -dM/dlambda values from 54.8 to 85.0 psec/nm . km . microm, significantly lower than that of fused silica (101 psec/nm . km . microm). These glasses show promise for waveguide fibers for the 3-4-microm region if ultrahigh purity specimens can be prepared.