Determination of Permittivity of Dielectric Analytes in the Terahertz Frequency Range Using Split Ring Resonator Elements Integrated with On-Chip Waveguide

Abstract

We investigate the use of finite-element simulations as a novel method for determining the dielectric property of target materials in the terahertz (THz) frequency range using split-ring resonator (SRR) sensing elements integrated into a planar Goubau line (PGL) waveguide. Five such SRRs were designed to support resonances at specific target frequencies. The origin of resonance modes was identified by investigating the electric field distribution and surface current modes in each SRR. Red-shifts were found in the resonances upon deposition of overlaid test dielectric layers that saturated for thicknesses above 10 µm. We also confirmed that the SRRs can work as independent sensors by depositing the analyte onto each individually. The relation between the permittivity of the target material and the saturated resonant frequency was obtained in each case, and was used to extract the permittivity of a test dielectric layer at six different frequencies in the range of 200–700 GHz as an example application. Our approach enables the permittivity of small volumes of analytes to be determined at a series of discrete frequencies up to ~1 THz.

Design of a Split Ring Resonator Integrated with On‐Chip Terahertz Waveguides for Colon Cancer Detection

“…Cancerous and healthy colonic tissues have permittivity values of 4.90 and 4.13 at the operating frequency of the SRR (f 0 = 596 GHz), respectively, while they have the same loss tangent of 0.0057 at f 0 . We note that, as previously reported, [10] the loss tangent value of the target material does not significantly affect the resonant frequency shift of the SRR, so weak resonances in loss tangent such as that seen at 550 GHz in the experimental data should not affect our conclusions.…”

“…[11] Various geometrical parameters in SRR and on-chip THz waveguides can be adjusted to optimize the performance of the chip depending on the applications. [10,12] Therefore, it is timely to explore methods to that could perform imaging of cancers with SRR integrated on-chip THz waveguides in order to maximize the detection sensitivity.…”

“…We recently showed that SRRs‐integrated with on‐chip THz waveguides can be used to detect target dielectric materials deposited on the chip, and the permittivity of unknown analytes determined at multiple frequencies. [ 10 ] Such systems could offer an ideal platform to examine target tissues inside the human body (e.g., in the colon) owing to their compactness [ 8 ] and good sensitivity to the water content. [ 11 ] Various geometrical parameters in SRR and on‐chip THz waveguides can be adjusted to optimize the performance of the chip depending on the applications.…”

A New Approach to Determining Liquid Concentration Using Multiband Annular Ring Microwave Sensor and Polarity Correlator

“…The flow of current in the resonators and the annular ring are in the form of parallel and anti-parallel direction which correspond to the control of electric and magnetic responses, respectively. These modes have been intensively studied for the manipulating of local field, nonlinearity and sensing [39][40][41][42]. This means that the sensor is sensitive to detecting minute changes in a liquid when placed on the hotspots shown by the electric field intensity.…”

Enhanced Terahertz Spectral‐Fingerprint Detection of α‐Lactose Using Sub‐Micrometer‐Gap On‐Chip Waveguides

“…[ 12 ] It is noteworthy that on‐chip THz systems can record spectra from small sample volumes relative to those used in free‐space THz‐TDS spectroscopy systems. [ 13 ] It is therefore interesting to investigate methods based on on‐chip THz waveguides that can further enhance their sensitivity for detecting spectra of materials.…”