3-D-Printed Terahertz Metamaterial Sensor With Polarization-Independent High-<i>Q</i> Resonance Based on Bound States in the Continuum

The application of 3-D printing in metamaterial production offers a streamlined alternative to the complex processes and expensive equipment of traditional micro- and nano-fabrication techniques, attracting attention for its simplicity and cost-effectiveness. This study experimentally validates a polarization-insensitive terahertz sensor based on bound states in the continuum (BICs). The sensor features an asymmetric configuration of cylindrical tetramers and is manufactured using a combination of 3-D printing and magnetron sputtering techniques. Achieving a high Q-factor resonance of 2489, the absorption mechanism of the sensor driven by quasi-BICs interaction is comprehensively explained through multipole decomposition. Analysis of surface current distribution and electromagnetic field reveals sharp absorption peaks with a near-field enhancement effect, suitable for sensing applications. Notably, the metasurface demonstrates a refractive index sensitivity of up to 544 GHz/RIU and a figure of merit (FOM) value of 1936. This fabrication method provided by 3-D printing offers a straightforward, efficient, and cost-effective means of producing terahertz metamaterials, showing promise for advancing terahertz metasurface applications in sensing detection.