We use several techniques to determine the refractive index of materials.
One of our unique setups is the Cryogenic Optical Test facility.
This facility has the capability for measuring the refractive index of materials with accuracies up to 10-6 at temperatures in the range of 35K – 400 K and wavelengths in the range of 250 nm – 25,000 nm, using different spectrophotometers.