Refractive-index measurements of zinc germanium diphosphide at 300 and 77 K by use of a modified Michelson interferometer.

A method to determine the absolute refractive index of materials available in the shape of flat wafers with parallel sides by using interferometric techniques is presented. With this method, nondestructive, sample-specific measurements can be made. The method is tested by using silicon, germanium and zinc selenide, and measurements for both the ordinary and extraordinary axes of ZnGeP2 for temperatures of 300 and 77 K are reported.