17 May 2016 High accuracy refractive index measurement system for germanium and silicon using the channelled spectrum method in the range of 3 to 15 μm
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Abstract
The refractive index of germanium is known only up to the third decimal according to publicly available sources. This data from various authors shows deviations in the order of several 10-3 not to be explained by experimental errors of the refractive index measurement. This is a strong indication that there is optically relevant material property variation. We present an interferometric method to measure the refractive index and its temperature dependency on etalon samples, which are cheaper to prepare with high quality than prism samples needed for the classical method of index measurement. Resolution and stability of our method is better than 10-4. The method can be used for both germanium and silicon. Our goal is to be able to produce material with optically relevant specifications. This is in contrast to the conventional method of specifying these important IR-optical materials in terms of electrical properties such as dopant type and concentration.
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Hilmar Straube, Hilmar Straube, Christian Hell, Christian Hell, } "High accuracy refractive index measurement system for germanium and silicon using the channelled spectrum method in the range of 3 to 15 μm", Proc. SPIE 9822, Advanced Optics for Defense Applications: UV through LWIR, 982208 (17 May 2016); doi: 10.1117/12.2238662; https://doi.org/10.1117/12.2238662
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