Measuring the refractive index of vitreous materials at cryogenic temperatures with a spectrometer

The use of a spectrometer to measure the refractive index of a prism glass sample in the visible and near-infrared regions at cryogenic temperature is reported. The details of the measuring cell and the experimental apparatus are provided, and a specific data reduction procedure based on ray tracing is introduced. Demonstrative results on a BK7 prism sample in a temperature range from 105 to 293 K and wavelength from 480 to 894 nm are presented. The measurement uncertainty is 3 × 10^-5 (2?).