Thin Dielectric Layers Evaluation Using Tunable Split-Ring Resonator Based Metasurface in THz Frequency Range

Abstract

The paper presents the evaluation of thin dielectric layers using a tunable split-ring resonator-based metasurface in the THz frequency range. Tunable unit cells of a metasurface allow its resonant frequency variation using some external excitation. This can be done in various ways. In this work, the behavior of such a metasurface is investigated by monitoring the resonant frequency value when the unit cell geometry is changed. Such behavior is utilized for the quality evaluation of a thin dielectric layer placed in vicinity of a metasurface. A change in dielectric permittivity noticeably affects the resonant frequency of a metasurface. In order to examine the state of the material under test, finite element method simulations were made for a 15 µm thin layer. As a result, the approximation-based relations between resonant frequencies (obtained for various geometries of structural element—in tunability range) and dielectric parameters of the examined material were derived. These relations carry more information than in the case of just one resonant frequency (the case of a non-tunable metasurface) and can be utilized for permittivity evaluation.

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“…Modern materials, creating the possibility of changing properties as a result of the influence of external factors and reconfiguration of their structure, became the subject of another work published in the Special Issue. Paper [10] explores the evaluation of thin dielectric layers in the THz frequency range using a tunable split-ring resonator-based metasurface. By changing the geometry of the metasurface's unit cells, the resonant frequency can be varied, allowing for the assessment of a nearby thin dielectric layer.…”