We describe an algorithm to extract the complex refractive index of a material from broadband reflectance and transmittance measurements taken by spectrophotometers. The algorithm combines Kramers–Kronig analysis with an inversion of Fresnel’s equations to provide a direct method of solving for the refractive index which is accurate, even for weakly absorbing materials, and easily applicable to radiative heat transfer calculations. The algorithm is validated by extracting the complex refractive index of polydimethylsiloxane between 0.25 μm and 100 μm and comparing against existing literature. We also discuss the importance of broadband optical properties to passive radiative cooling and details of the uncertainty analysis of the algorithm.

中文翻译：

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从分光光度测量中提取宽带复折射率的直接方法：聚二甲基硅氧烷被动辐射冷却的应用

我们描述了一种从分光光度计进行的宽带反射率和透射率测量中提取材料的复折射率的算法。该算法将 Kramers-Kronig 分析与菲涅尔方程的反演相结合，提供了一种直接求解折射率的方法，即使对于弱吸收材料，该方法也是准确的，并且易于应用于辐射传热计算。通过提取 0.25 μm 至 100 μm 之间的聚二甲基硅氧烷的复折射率并与现有文献进行比较，对该算法进行了验证。我们还讨论了宽带光学特性对被动辐射冷却的重要性以及算法不确定性分析的细节。