Withayachumnankul Withawat, Fischer Bernd M, Abbott Derek
School of Electrical & Electronic Engineering, The University of Adelaide, Adelaide, SA 5005, Australia.
Opt Express. 2008 May 12;16(10):7382-96. doi: 10.1364/oe.16.007382.
The thickness of a sample material for a transmission-mode terahertz time-domain spectroscopy (THz-TDS) measurement is the subject of interest in this paper. A sample that is too thick or too thin can raise the problem of measurement uncertainty. Although greater thickness allows the terahertz radiation--or T-rays--to interact more with bulk material, the SNR rolls off with thickness due to signal attenuation. A sample that is too thin renders itself nearly invisible to T-rays, in such a way that the system can hardly sense the difference between the sample and a free space path. The optimal trade-off is analyzed and revealed in this paper, where our approach is to find the optimal thickness that results in the minimal uncertainty of measured optical constants. The derived model for optimal thickness is supported by the results from experiments performed with polyvinyl chloride (PVC), high-density polyethylene (HDPE), and lactose samples.
本文关注用于透射模式太赫兹时域光谱（THz-TDS）测量的样品材料厚度。过厚或过薄的样品都会引发测量不确定度问题。尽管较大的厚度能使太赫兹辐射（即T射线）与块状材料有更多相互作用，但由于信号衰减，信噪比会随厚度降低。过薄的样品对T射线几乎不可见，以至于系统很难分辨样品与自由空间路径之间的差异。本文分析并揭示了最佳权衡点，我们的方法是找到能使测量光学常数的不确定度最小的最佳厚度。聚氯乙烯（PVC）、高密度聚乙烯（HDPE）和乳糖样品的实验结果支持了所推导的最佳厚度模型。
