van Frank Sandrine, Leiss-Holzinger Elisabeth, Pfleger Michael, Rankl Christian
Research Center for Non-Destructive Testing GmbH (RECENDT), Altenberger Straße 69, 4040 Linz, Austria.
Sensors (Basel). 2020 Jun 12;20(12):3352. doi: 10.3390/s20123352.
Terahertz time-domain spectroscopy is a useful technique to characterize layered samples and thin films. It gives access to their optical properties and thickness. Such measurements are done in transmission, which requires access to the sample from opposite sides. In reality this is not always possible. In such cases, reflection measurements are the only option, but they are more difficult to implement. Here we propose a method to characterize films in reflection geometry using a polarimetric approach based on the identification of Brewster angle and modeling of the measured signal to extract the refractive index and thickness of the sample. The technique is demonstrated experimentally on an unsupported single layer thin film sample. The extracted optical properties and thickness were in good agreement with established transmission terahertz spectroscopy measurements. The new method has the potential to cover a wide range of applications, both for research and industrial purposes.
太赫兹时域光谱技术是一种用于表征分层样品和薄膜的有用技术。它可以获取样品的光学性质和厚度。此类测量是在透射模式下进行的，这需要从样品的两侧进行测量。实际上，这并不总是可行的。在这种情况下，反射测量是唯一的选择，但实施起来更加困难。在此，我们提出一种方法，基于布儒斯特角的识别和对测量信号的建模，利用偏振方法在反射几何结构中表征薄膜，以提取样品的折射率和厚度。该技术已在无支撑的单层薄膜样品上进行了实验验证。提取的光学性质和厚度与已有的透射太赫兹光谱测量结果吻合良好。这种新方法具有广泛的应用潜力，可用于研究和工业目的。
