Refractive Index, Density and Polarizability of Silica Glass with Various Fictive Temperatures

The refractive index and density of silica glass were measured for various fictive temperatures. They both increase without any local maxima, as the fictive temperature increases up to 1550°C. From the relationship between the refractive index and the density, polarizability was estimated using the Lorentz-Lorenz formula. The polarizability decreases with increasing density, while the refractive index increases. The variation in refractive index with fictive temperature depends on changes in not only the density but also the polarizability. The polarizability was found to contribute to the variation in refractive index to the extent of about one half of that from the density. With increasing density, the refractive index at a longer wavelength increases at a higher rate, which originates from a lower rate of decrease in polarizability at a longer wavelength.