On-Chip Characterization of High-Loss Liquids between 750 GHz and 1100 GHz

TL;DR

This paper introduces a sensitive on-chip terahertz spectroscopy method capable of measuring the complex permittivity of highly lossy liquids like water in the 750-1100 GHz range, overcoming previous signal loss challenges.

Contribution

The paper presents a novel on-chip terahertz spectroscopy technique that effectively characterizes high-loss liquids such as water at frequencies up to 1100 GHz.

Findings

Accurately measured permittivities of water and alcohol solutions.

Method successfully operates in the 750-1100 GHz frequency range.

Results align well with existing literature data.

Abstract

Terahertz spectroscopy is a promising tool for analyzing the picosecond dynamics of biomolecules, which is influenced by surrounding water molecules. However, water causes extreme losses to terahertz signals, preventing sensitive measurements at this frequency range. Here, we present sensitive on-chip terahertz spectroscopy of highly lossy aqueous solutions using a vector network analyzer, contact probes, and a coplanar waveguide with a 0.1 mm wide microfluidic channel. The complex permittivities of various deionized water/isopropyl alcohol concentration are extracted from a known reference measurement across the frequency range 750-1100 GHz and agrees well with literature data. The results prove the presented method as a high-sensitive approach for on-chip terahertz spectroscopy of high-loss liquids, capable of resolving the permittivity of water.