Uncertainty in terahertz time-domain spectroscopy measurement

TLDR

Terahertz time‑domain spectroscopy has been widely used to measure optical constants at terahertz frequencies, yet systematic analysis of measurement errors remains absent. The study aims to perform a comprehensive analysis of measurement uncertainty in THz‑TDS systems. The authors identify error sources in terahertz spectrometers and the parameter‑estimation process, and quantify each source’s impact on the derived optical constants using physical models. The resulting analytical uncertainty model is validated against experimental THz‑TDS data.

Abstract

Measurements of optical constants at terahertz—or T-ray—frequencies have been performed extensively using terahertz time-domain spectroscopy (THz-TDS). Spectrometers, together with physical models explaining the interaction between a sample and T-ray radiation, are progressively being developed. Nevertheless, measurement errors in the optical constants, so far, have not been systematically analyzed. This situation calls for a comprehensive analysis of measurement uncertainty in THz-TDS systems. The sources of error existing in a terahertz spectrometer and throughout the parameter estimation process are identified. The analysis herein quantifies the impact of each source on the output optical constants. The resulting analytical model is evaluated against experimental THz-TDS data.