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

摘要

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