Wavefront sensing applied to determine the temperature dependence of the refractive index of liquids.

A method based on wavefront sensing is described to determine the temperature dependence of the refractive index of liquids. The technique only implies measuring the wavefront of a light beam passing through a micro-vessel containing the liquid. Here, this vessel is a crater made by CO2 laser processing in a fused silica plate. From the wavefront analysis, the optical path that is related to the refractive index of the liquid can be determined. This measurement can be done at different temperatures to obtain the temperature dependence of the refractive index. This method is applied to three liquids: water, ethanol, and cyclohexane at λ=630 nm. The results show a linear dependence in the range of 17°C-50°C and give coefficients dndT that are in good agreement with values from the literature.