Temperature dependence of refractive index of glassy SiO2 in the infrared wavelength range

An interferometric method was used for the determination of refractive index of glassy SiO2 in the infrared (LR) wavelength region (1.44 < lambda < 4.77 mu m) at temperatures ranging from 23.5 to 481 degrees C by IR spectroscopy. The refractive index was found to increase with temperature at a given wavelength. Irregularities of the thermal coefficient of the refractive index (dn/dT) with temperature were observed and explained by the existence of crystal-like microstructures in silica glass. Optical dispersion (dn/d lambda) exhibits a maximum at a given temperature. The wavelength at the maximum depends on temperature, showing irregularities with temperature like the thermal coefficient of refractive index. (C) 2000 Elsevier Science Ltd. All rights reserved.