Extraction of optical parameters of composite materials for real-world THz application

Abstract

Terahertz time-domain spectroscopy has emerged as a competent technique for real-world applications such as quality control in pharmaceutical and food industry, biomedical and precision-agriculture. However, investigating the optical response of the practical composite samples such as pharmaceutical tablets, biological composites and nano-composites using Terahertz (THz) time-domain spectroscopy (TDS) is quite challenging. In the present work, we have prepared two series of binary composites, with different volume fraction of constituent materials. These composites were probed using pulsed THz TDS and their dielectric response was modeled using the effective medium theory (EMT). Based on the volume fraction of the constituent material, three EMT models, including Maxwell-Garnet (MG), Polder-van-Santen (PvS) and Landau-Lifshitz-Looyenga (LLL), were compared empirically with the conventional analysis at different frequencies; and the accuracy and ambiguity of the extracted parameters using these quasi-static models were determined. Hence, the feasibility study of these theoretical models was discussed to assess their practicality.