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arXiv · 2606.26971

Refractive indices of Y$_2$SiO$_5$ in the near-infrared

Shijun Zhang·Jérôme Debray·Benoît Boulanger·Pierre Lemonde·Thierry Chanelière
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Abstract

Y$_2$SiO$_5$ is a reference birefringent material for optical quantum technologies. The refractive index is primarily known in the visible spectrum, whereas this crystal is also used in the near-infrared. We begin by analysing historical measurements, as well as the modelling proposed at the time. The absence of refractive index tabulated values in the near- and mid-infrared ranges motivated us to carry out independent measurements. Using interferometric techniques in the telecom wavelength range, we demonstrate the ability to determine the principal refractive indices and propose a model spanning a broad spectral range based on Sellmeier equations for which we explicitly give the coefficients and discuss the achievable accuracy. Conversely, as an illustration, white-light interference enables us to precisely determine the thickness of a Y$_2$SiO$_5$ thin film on the order of ten micrometers.

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Shijun Zhang, Jérôme Debray, Benoît Boulanger, Pierre Lemonde, Thierry Chanelière. 2026-06-25. Refractive indices of Y$_2$SiO$_5$ in the near-infrared. https://doi.org/10.1364/ome.609366

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