Spectral-domain tandem interferometry to measure the group dispersion of optical samples

A spectral-domain technique based on tandem interferometry is used for measuring the group dispersion of optical samples over a wide wavelength range. The technique utilizes a tandem configuration of a Michelson interferometer and an unbalanced Mach–Zehnder interferometer with a sample inserted into its test arm. First, the theoretical background of the technique is presented and then experiments with individual interferometers and their tandem configuration are specified. In all the experiments the spectral signals are recorded to measure the equalization wavelength as a function of the path length difference, or equivalently the group dispersion. We measure the group refractive index as a function of wavelength for a glass sample of known thickness and for a quartz crystal as well.