Frequency‐Resolving Terahertz Detection via NbGeSb Topological Semimetal Integrated With Multi‐Scale 3D‐Printed Metastructures

Frequency‐resolving terahertz (THz) detection is critically needed for 6G frequency‐multiplexed receivers, yet remains largely unrealized with conventional broadband detectors. Here, we demonstrate a frequency‐resolving THz detection concept that integrates NbGeSb topological semimetal thin films with multi‐scale 3D‐printed subwavelength metastructures. Three distinct unit‐cell dimensions (S: 200/170 × 240 µm 2 , M: 240/210 × 260 µm 2 , L: 280/250 × 300 µm 2 ) create size‐dependent localized surface plasmon resonance (LSPR) channels, enabling selective field confinement across 0.1–0.4 THz. Finite‐difference simulations reveal a peak field enhancement exceeding 10 3 at 0.1 THz for the large‐area device, with progressive spectral detuning toward higher frequencies—establishing the physical basis for frequency‐resolving detection. At room temperature and 11.5 V bias, the optimized device delivers a responsivity of 42.231 A/W and a noise‐equivalent power (NEP) of 1.191 pW/Hz 1/2 . THz time‐domain spectroscopy directly confirms frequency‐selective modulation, with the strongest response near 0.1 THz and monotonic variation across the spectral range. Separate laser and magnetic‐field modulation each enhance frequency‐selective contrast without generating new off‐resonance channels, and their simultaneous use is proposed for future cooperative operation. These results establish multi‐scale 3D‐printed metastructures as a practical platform for frequency‐resolving THz detection, offering a compact route toward spectrally discriminating THz receivers for next‐generation communication and sensing systems.