Measuring the temperature variation of refractive index of water by digital interferometry for manufacturing an optical dosimeter

Using coherent light sources for manufacturing optical dosimeters is of considerable interest. Optical dosimeters are mostly employed for radiotherapy applications; where knowing the temperature dependency of refractive index of the used material in the core of dosimeter, often water, is required. In this work, by setting up and employing an interferometer in the laboratory, the temperature dependency of refractive index of water is measured. The setup is fully described and the required theoretical relations for interpreting the experimental data are developed. Comparing the results with the previous experimental data provided by other groups, demonstrats good compromise and confirms the accuracy of the measurements. It is shown that the second-order polynomial model can be efficiently used for interpreting the measurement data. The results of this study can be used in all those applications where knowing the temperature dependency of refractive index of water is a prerequisite.