Citation:
Daniel Francis, Helen D. Ford and Ralph P. Tatam. Spectrometer-based refractive index and dispersion measurement using low-coherence interferometry with confocal scanning. Optics Express, 2018, Vol. 26, Issue 3, pp. 3604-3617
Abstract:
This paper describes a technique for measuring refractive index and thickness of
transparent plates using a fibre-optic low-coherence interferometer. The interferometer is used to
independently measure quantities related to the phase and group refractive indices, np and ng,
of the material under investigation. Additionally, the dispersion of the phase index dependent
quantity is measured by taking advantage of the range of wavelengths available from a broadband
source. These three quantities are related to simultaneously yield np and ng as well as the
geometrical thickness t of the sample. Measurements are presented for a range of transparent
materials including measurements of the ordinary and extraordinary refractive indices of a
birefringent sapphire window. The mean percentage errors across all the samples tested were 0.09% for np, 0.08% for np, and 0.11% for t.