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 of 400–1550 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 in the 400–1050 nm range, a homemade transmission grating spectrometer that measures the interferogram in the 950–1550 nm near infrared range, 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 10−4 in the refractive index after fitting it with the Cauchy formula.