Refractive index measurements of ten germanium samples

The refractive index of germanium was measured for ten samples, covering the various crystal types, over the 8-14-microm wavelength range. Samples were obtained from several suppliers, and differences between samples in the index values reported were not significant compared with the estimated index uncertainties of +/-0.0003. Three samples were examined at two laboratories to act as a check on the absolute values obtained. A temperature coefficient index of 0.00040 degrees C(-1) was obtained for the 20-25-C range.