Polarization-Independent Anapole Metasurfaces for Terahertz Signal Processing

Anapole resonance has recently attracted increasing attention due to its non-radiating characteristics. However, sui nanostructures supporting anapole resonance still need to be found, and its practical applications remain largely unexplored. At the same time, the development of miniaturized, high-performance devices for terahertz-band signal processing, such as filters and modulators, remains limited. This lack of progress significantly hinders advancements in fields such as terahertz communications and imaging. In this study, we designed a novel metasurface structure (capacitor mesh) that supports anapole resonance. This structure exhibits strong polarization independence, high incident angle insensitivity, topological connectivity, and tunable resonance frequency through geometric parameter adjustments. Using this metasurface, we proposed and implemented a terahertz bandpass filter with a designed center frequency of 0.4 THz. Due to its anapole resonance properties, the device offers significant advantages in minimizing reflection loss. It was fabricated and characterized, with transmittance spectra revealing low energy loss (28%) at the center frequency of 0.39 THz and a bandwidth of 60 GHz. Additionally, we demonstrated the metasurface's potential for use in terahertz modulators. Our work underscores the significant potential of anapole resonance in terahertz field manipulation and terahertz devices.