Terahertz Metamaterial Composed of Subwavelength Metal Layer – Porous Insulator – Metal Layer for Humidity Sensing

Terahertz (THz) spectroscopy offers a non-contact analysis of biological samples; however, it faces challenges due to water absorption within the THz range. To address this issue, a THz metamaterial sensor was developed for high-sensitivity moisture measurements. The sensor is composed of a subwavelength metal layer, porous insulator, and metal layer, with its principle relying on resonant frequency shifts derived from changes in capacitance with and without the target gas within the porosity. The sensor experimentally demonstrated a significant frequency shift in response to humidity compared to the simulation results, indicating enhanced sensitivity because of the porous structure. This novel approach has the potential for practical analysis using THz waves.