Metamaterial near-field sensor for deep-subwavelength thickness measurements and sensitive refractometry in the terahertz frequency range

TL;DR

This paper introduces a metamaterial-based terahertz sensor capable of ultra-precise subwavelength thickness measurements and sensitive refractometry, utilizing Fano resonance shifts for high-resolution detection.

Contribution

The work presents a novel THz metamaterial sensor that achieves nanometer-scale thickness resolution and high refractive index sensitivity, supported by an analytical model.

Findings

Minimum thickness resolution of 12.5 nm

Refractive index sensitivity of 0.43 THz per RIU

Analytical model accurately describes resonance dependence

Abstract

We present a metamaterial-based terahertz (THz) sensor for thickness measurements of subwavelength-thin materials and refractometry of liquids and liquid mixtures. The sensor operates in reflection geometry and exploits the frequency shift of a sharp Fano resonance minimum in the presence of dielectric materials. We obtained a minimum thickness resolution of 12.5 nm (1/16000 times the wavelength of the THz radiation) and a refractive index sensitivity of 0.43 THz per refractive index unit. We support the experimental results by an analytical model that describes the dependence of the resonance frequency on the sample material thickness and the refractive index.