Pfleger Michael, Roitner Heinz, Pühringer Harald, Wiesauer Karin, Grün Hubert, Katletz Stefan
Appl Opt. 2014 May 20;53(15):3183-90. doi: 10.1364/AO.53.003183.
Polarization-sensitive (PS) terahertz (THz) technology can be used for investigating anisotropic materials that are opaque for visible light. A full characterization of an anisotropic material requires the extraction of the birefringence as well as the orientation of the optical axis from the measurement data. We present an approach based on THz time-domain spectroscopy (TDS) that exploits the spectral content of the THz signal for determining these two parameters from only two measurements. In contrast to an earlier approach with a more sophisticated PS-THz system and quasi-circularly polarized THz radiation, now a simple standard THz-TDS system can be employed. After a description of the mathematical model for data analysis we demonstrate the applicability of our method for a lithium niobate crystal and furthermore for a glass-fiber reinforced polymer sample, for which the orientation of the optical axis and birefringence are obtained in a spatially resolved way, showing the potential of the method also for PS-THz imaging. As no specialized setup or components are required, our approach can be easily and extensively applied for the analysis of anisotropic samples at THz frequencies.
偏振敏感（PS）太赫兹（THz）技术可用于研究对可见光不透明的各向异性材料。对各向异性材料进行全面表征需要从测量数据中提取双折射以及光轴方向。我们提出一种基于太赫兹时域光谱（TDS）的方法，该方法利用太赫兹信号的光谱内容仅通过两次测量来确定这两个参数。与早期使用更复杂的PS - THz系统和准圆偏振太赫兹辐射的方法不同，现在可以使用简单的标准太赫兹 - TDS系统。在描述了数据分析的数学模型之后，我们证明了我们的方法对铌酸锂晶体以及玻璃纤维增强聚合物样品的适用性，对于这些样品，以空间分辨的方式获得了光轴方向和双折射，这也展示了该方法在PS - THz成像方面的潜力。由于不需要专门的装置或组件，我们的方法可以轻松且广泛地应用于太赫兹频率下各向异性样品的分析。
