In this work, the challenges of terahertz (THz) time-domain spectroscopy on complex (multilayer) samples with time-varying (dynamic) characteristics are addressed. The challenges appear in characterizations of the refractive index and extinction coefficient, as etalon artifacts due to internal reflections, and are accentuated in multilayer structures having dynamic and low-loss materials, such as biomolecular materials. This is because nonidealities may form as airgaps at the interfaces and as inhomogeneity in the bulk. The proposed methodology addresses the challenges by introducing a generalized model that accommodates dynamic formation of airgaps and inhomogeneity. It is shown that the generality of the model allows it to mitigate etalon artifacts and yield a highly accurate representation of the material characteristics, with low systematic error, even for low-loss materials. The methodology is applied to characterizations of quartz and glucose in the THz spectrum to see fine detail in the characteristics of quartz and the crystallization of glucose.

中文翻译：

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通过太赫兹时域光谱进行动态材料表征的方法

在这项工作中，解决了太赫兹 (THz) 时域光谱对具有时变（动态）特性的复杂（多层）样品的挑战。挑战出现在折射率和消光系数的表征中，因为内部反射导致标准具伪影，并且在具有动态和低损耗材料（例如生物分子材料）的多层结构中更加突出。这是因为非理想性可能形成为界面处的气隙和体中的不均匀性。所提出的方法通过引入适应气隙和不均匀性动态形成的通用模型来解决这些挑战。结果表明，该模型的通用性使其能够减轻标准具伪影并产生对材料特性的高度准确的表示，具有低系统误差，即使对于低损耗材料也是如此。该方法应用于太赫兹光谱中石英和葡萄糖的表征，以查看石英特性和葡萄糖结晶的精细细节。