Spectrally resolved white light interferometer for measuring dispersion in the visible and near infrared range

Abstract

We design a spectrally resolved interferometer to measure the refractive index of transparent samples over a broad spectral range between 400 and 550 nm. The measuring device consists of a Michelson interferometer whose output is analysed by means of three fibre spectrometers: a homemade prism spectrometer which obtains the interferogram generated by the sample between 400 and 1050 nm, a homemade transmission grating spectrometer that measures the interferogram in between 950 and 1550 nm, and a commercial Czerny Turner spectrometer used to make high precision measurements of the displacement between the Michelson mirrors. The whole system is illuminated by a white light source with an emission spectrum similar to that of a black body. We test the instrument on solid and liquid samples achieving accuracy of up to 0.0001 in the refractive index after fitting it with the Cauchy formula.