Unlock a novel dimension of terahertz metalens engineering

Quasicrystals, characterized by their aperiodic lattice sites and high-order rotational symmetry, to the best of our knowledge provide a novel design dimension for photonics that transcends the limitations of traditional crystals. This study capitalizes on these unique features to present a numerical investigation of a broadband terahertz metalens based on a Penrose P3 quasicrystalline structure and Pancharatnam-Berry phase manipulation. The proposed metalens exemplifies the synergistic integration of high-order symmetry, topological protection, and broadband focusing on a metasurface. It achieves this by strategically positioning rotatable silicon nanopillars at the lattice points of the quasicrystalline structure, utilizing their fivefold rotational symmetry and aperiodicity. Due to its aperiodic topological characteristics, the device spontaneously generates tenfold symmetric diffraction patterns in the far field, thereby breaking the symmetry constraints inherent in periodic structures. Within a 0.6 THz operational bandwidth, the metalens demonstrates efficient focusing capabilities and maintains stability under wide-angle illumination. This work achieves the integration of quasicrystalline high-order symmetry, topological robustness, and broadband focusing within a single metasurface. This work offers a new dimension for applications in terahertz imaging, communication, and integrated optics, thereby advancing the practical development of aperiodic topological photonics.