Spoof Surface Plasmon-Based Coplanar Waveguide Sensor for Dielectric Sensing Applications

A highly confined spoof surface plasmon (SSP) based sensor to test the dielectric materials in microwave and terahertz (THz) frequency region is presented. The proposed sensor comprised of the main coplanar waveguide (CPW) line and the defected T-shaped SSP line at the top and bottom of the substrate, respectively. The defect in the SSP line provides stop band, and hence localization of the transmission energy at the defect location. The resonance frequency and localization of the transmission energy can primarily be tuned by varying the height of the defect and the periodicity of the SSP strip. The proposed sensor is numerically optimized and tested in the microwave and THz frequency region using the full wave electromagnetic solver (CST-MWS). The designed sensor conforms the planar geometry, which facilitates its ease of integration to the modern radio frequency (RF) and THz frequency systems. The sensor prototype is fabricated and experimentally tested in the microwave frequency region using a number of standard solid and liquid samples. It is found that the test samples with closely spaced dielectric constant can easily be distinguished using the developed SSP sensor owing to its considerably high quality factor (~165) and hence high resolution. Additionally, the fabricated compact sensor prototype has adequate sensitivity (2.84%) and small sensing area, as a result it helps to test small volume of liquid specimen (order of few microliter), which is generally the case with the biological samples due to their low volume availability.