Sensitive interferometer for determination of optical and thermal properties

A very sensitive interferometric technique is presented. It allows direct measurement of optical and thermal properties. The experimental set-up is very simple and acts essentially as an unfocused Fabry-Perot interferometer giving rise only to a central fringe. Measurement of (∂n/∂T)_p up to 10^-7 K^-1 is possible. Determination of (∂n/∂T)_p for some liquids, particularly for water and deuterium oxide, has been already performed and others, for ionic crystals, are under way.