E-shaped split ring resonator used for metasurface-based structure with an ultra-high Q-factor for terahertz application

Plasmonic devices based on split ring resonator (SRR) of ultra-low-loss performance (high Q-factor) are significant for a broad range of applications and studies. However, due to the inevitable ohmic and radiation losses, it has always been a challenge to design various types of plasmonic devices with high Q-factor. Here, we theoretically present a unique E-shaped SRR that can destructively suppress dipole radiation by adjusting the grating-arm position to produce asymmetry. Meanwhile, the proposed terahertz metasurface structure formed by periodically arranged E-shaped SRRs can give rise to high Q-factor resonances. The results show that an ultra-high Q-factor beyond 104 can be obtained in the terahertz frequency region by optimizing the structural parameters. The sensing characteristics of such a metasurface-based structure served as a refractive-index sensor are investigated as well, demonstrating its advantage of high sensitivity. Unique radiation properties of the metasurface-based structure enable it to use in the design of novel low-loss, ultra-sensitive sensors, narrowband filters, and other plasmonic devices.