Unveiling the origin of spurious features in THz-TDS of powder compacts
File(s)
Accepted version
Author(s)
Gorecki, Jon
Murphy, Keir N
Markl, Daniel
Burnett, Andrew D
Naftaly, Mira
Type
Journal Article
Abstract
Terahertz time-domain spectroscopy (THz-TDS) is a vital tool for scientific and industrial analysis, however, many commonly analysed products, such as those found in pharmaceutical, agriculture, and mining sectors, are produced as powders or granular materials, and these sample morphologies have been reported to produce anomalous spectral features which can often obscure known material resonances. The cause of these anomalous features has been poorly understood, making it difficult to predict their presence and limiting the applicability of THz-TDS for such materials. Here we systematically study how the sample morphology of granular compacts produces anomalous spectral features by performing extensive experimental measurements on two-part powder compacts with varying microsphere size and concentration. Further, we employ ray-tracing simulations to identify the physical mechanism whereby these spectral features arise owing to variations in optical path length within the heterogeneous sample. We believe this is the first time that the physical cause of spurious spectral features within powder samples has been adequately explained and that a robust method has been presented for modeling this effect. By understanding these features, we propose that instead of being seen as a parasitic effect, their presence can be utilised to extract morphological properties of the samples, thereby enhancing the utility of THz-TDS for granular materials.
Date Issued
2025-05-01
Date Acceptance
2025-03-01
Citation
IEEE Transactions on Terahertz Science and Technology, 2025, 15 (3), pp.418-430
ISSN
2156-342X
Publisher
Institute of Electrical and Electronics Engineers
Start Page
418
End Page
430
Journal / Book Title
IEEE Transactions on Terahertz Science and Technology
Volume
15
Issue
3
Copyright Statement
Copyright © 2025 IEEE. This is the author’s accepted manuscript made available under a CC-BY licence in accordance with Imperial’s Research Publications Open Access policy (www.imperial.ac.uk/oa-policy)
License URL
Publication Status
Published
Date Publish Online
2025-03-10