A New Metric for the Comparison of Permittivity Models in Terahertz Time-Domain Spectroscopy

We present a robust method, as well as a new metric, for the comparison of permittivity models in terahertz timedomain spectroscopy (THz-TDS).In this work, we show that the signal is perturbed by a deterministic part that has to be either modeled or removed.Therefore, we perform an extensive perturbation/noise analysis of a THz-TDS system, we remove and model the unwanted deterministic perturbation/noises and implement them into our fitting process.This new method has now been implemented in our open-source software, Fit@TDS, available at : https://github.com/THzbiophotonics/Fit-TDS.This work is the first step towards the derivation of uncertainties, and therefore the use of error bars.We hope that this will lead to performing analytical analysis with THz-TDS, as results obtained from different setups will be comparable.Finally, we apply this protocol to the study of a α-lactose monohydrate pellet in order to give more insight on the molecular dynamics behind the absorption peaks.The comparison with simulation results is made easier thanks to the probabilities derived from the metric.