Band‐Selective, Low‐Dispersion Terahertz Attenuators Based on 3D Bulk Metamaterials Leveraging De‐latticed Cross‐Bar Resonator Ensembles

ABSTRACT

Terahertz (THz) optical components for power attenuation and dispersion management require materials that provide isotropic and band‐selective control of electromagnetic waves. However, two‐dimensional (2D) metasurfaces based on coherent lattice coupling exhibit polarization anisotropy and angular dispersion, which lead to phase distortion. Here, three‐dimensional (3D) bulk metamaterials (MMs) functioning as THz attenuators are proposed and experimentally demonstrated based on a de‐latticing strategy inspired by amorphous natural materials. Periodic arrays of cross‐bar meta‐atoms are encapsulated by cyclo‐olefin polymer (COP) as randomly oriented cubic meta‐grains and dispersed within a COP matrix, forming an amorphous composite that eliminates in‐plane coherence. The fabricated samples exhibit band‐selective and thickness‐tunable attenuation with a smooth refractive‐index variation across 0.3–0.4 THz. Compared with the 2D metasurface, the dispersion slope decreases from 8.37 to 0.36 at the resonant frequency, indicating an order‐of‐magnitude suppression of phase dispersion. The attenuation scales continuously with thickness owing to incoherent resonant scattering from randomly oriented dipoles, providing a practical pathway to thickness‐dependent and band‐selective response. This work demonstrates an isotropic, low‐dispersion, and thickness‐tunable 3D bulk MMs THz attenuator that overcomes the polarization anisotropy and strong dispersion of conventional 2D attenuators, offering a practical pathway toward integrated THz photonic systems.