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Comparison of various optical characterization techniques for the surface analysis of optical-grade germanium infrared materials

Optimization of the optical quality of optical-grade germanium components requires an in-depth investigation of the different contributions to the optical loss in germanium. In this paper we therefore focus on this optical characterization. We give an overview of possible characterization techniques to determine surface roughness, surface/bulk absorption and refractive index inhomogeneities and we highlight the obtained optical characteristics. To conclude we select the most appropriate non-destructive characterization tool for each optical parameter.