Abstract: The Index Interferometric Instrument is a highly accurate instrument which can be utilized to measure the index of refraction, the dispersion, and the index profile of materials. The instrument provides the data necessary to measure the index of refraction of materials to five significant figures. The index profile can be measured at any chosen wavelength without any sample preparation. The instrument utilizes a 10 nm to a 400 nm bandwidth light source and a light source with a bandwidth of less than 10 nm in combination with an interferometer. Each light source creates interference patterns from the sample and a reference mirror which can be used to accurately calculate the index of refraction of an entire sample at any given point on the sample.