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    Herbicide/pesticide sensing with metamaterial absorber in THz regime
    (Elsevier B.V., 2021) Tantiwanichapan, Khwanchai; Durmaz, Habibe
    Terahertz (THz) technology has been attracted great interest in many research areas over the years, especially THz plasmonics for sensing applications since intra- and inter-molecular vibrations are within the THz range. The sensitivity of free-space THz detection can be boosted up by use of metamaterials (MM), which are artificial structures in subwavelength scale of the incident light. These artificial materials present high electric field enhancement and high sensitivity to the change in their surroundings. In this article, residual herbicides/pesticides have been investigated both theoretically and experimentally with a polarization-insensitive THz metamaterial absorber (MMA) composed of dielectric-metal disk antennas. Our THz MMA can detect as small as 5 ppM of commonly used herbicide/pesticide, namely paraquat and glyphosate. The results show that sensitivity is greatly improved by using THz MMA, with the limit of detection (LOD) of these herbicides/pesticides reaching to 5 ppM. These results indicate that THz MMA platform could be a valuable method for highly sensitive THz applications in food quality and safety control. We believe, our sensor platform based on general c-mos technology fabrication could be a potential detection tool for herbicides/ pesticides residues in agriculture and food products.
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    Improvement of response time and heat transfer capacity of metamaterial absorber for terahertz detector applications
    (Institute of Electrical and Electronics Engineers Inc., 2023) Tantiwanichapan, Khwanchai; Durmaz, Habibe
    We have introduced a THz metamaterial absorber system that consists of a metal disk antenna connected to successive dielectric and metal layers via a metal rod. The heat transfer speed and capacity of the proposed platform with a metal rod inserted through the dielectric layer have been numerically studied for the first time in this work. The proposed THz metamaterial absorber system can improve the heat transfer capacity 0.7 K/s compared to without a metal rod situation. The simulation proves that heat transfer can be achieved in the proposed absorber less than 10 μs times compared to without a metal rod case. The simulation results indicate the absorption strength of the metamaterial absorber is almost independent of the rod depth. This detector system will be remarkably beneficial for imaging applications where fast heat-signal conversion is necessary.