Review of thermal infrared polarimetry, part 2: experiment

Abstract

After the discussion on thermal polarization theory from part 1 of this review, we now review practical methods for experimentally measuring infrared polarization properties. Starting with a model for thermal emission from inhomogeneous media, we discuss the complexities of paints and how to determine the ideal thickness of paints used for blackbody simulators. Another commonly used inhomogeneous material is anodized aluminum, and we provide an extensive discussion of its fascinating structure and its optical properties in the thermal infrared. Theoretical analysis and experimental measurements show how the peculiar properties of alumina in the longwave infrared region combine to create a material that has a surprisingly high emissivity, for optically smooth sapphire and highly inhomogeneous anodize-coated aluminum. To illustrate features of thermal polarization theory given in part 1 of this review, we also present a series of infrared polarization images, and demonstrate the use of a convenient reference source for thermal polarization testing.