Terahertz Measurements Through Water Enabled by a Compact and Cost-Efficient THz-TDS System

Spectroscopy is a widely used tool for material characterization and classification across all frequencies of the electromagnetic spectrum. Depending on the frequency employed, absorption losses become the limiting factor for the penetration depth of the material under test (MUT). Water, in particular, exhibits strong absorption in the terahertz range, necessitating extended averaging times. In this study, we present terahertz time-domain spectroscopy (THz-TDS) measurements conducted across varying thicknesses of water, using our self-built, compact measurement system, which maintains phase stability over pro-longed averaging periods achieving a peak dynamic range grater than 130 dB.