Terahertz sensing of highly absorptive water-methanol mixtures with multiple resonances in metamaterials

TL;DR

This paper presents a cost-effective metamaterial-based terahertz sensor capable of highly sensitive detection of water-methanol mixtures, overcoming water's strong terahertz absorption through multiple resonances.

Contribution

The study introduces a simple asymmetric wire metamaterial supporting multiple resonances for enhanced terahertz sensing of highly absorptive solutions.

Findings

Resonance sensitivities of 160 and 305 GHz/RIU for water-methanol mixtures.

Demonstrated effective detection of highly absorptive chemical solutions.

Utilized multiple resonances to improve sensing accuracy.

Abstract

Ultrasensitive terahertz sensing of highly absorptive aqueous solutions remains challenging due to strong absorption of water in the terahertz regime. Here, we experimentally demonstrate a cost-effective metamaterial-based sensor integrated with terahertz time-domain spectroscopy for highly absorptive water-methanol mixture sensing. This metamaterial has simple asymmetric wire structures that support multiple resonances including a fundamental Fano resonance and higher order dipolar resonance in the terahertz regime. Both the resonance modes have strong intensity in the transmission spectra which we exploit for detection of the highly absorptive water-methanol mixtures. The experimentally characterized sensitivities of the Fano and dipole resonances for the water-methanol mixtures are found to be 160 and 305 GHz/RIU, respectively. This method provides a route for readily available metamaterial-assisted terahertz spectroscopy for ultrasensitive sensing of highly absorptive chemical and biochemical materials with multiple resonances and high accuracy.