Cryogenic beam-splitting metamaterial platform: static superconducting and dynamic composite architectures

The rapid development of cryogenic terahertz (THz) systems has placed unprecedented demands on core beam-splitter components: they must simultaneously deliver dynamic tunability, multi-channel processing, and ultra-low loss characteristics in extreme environments. Although conventional noble metals exhibit excellent conductivity at these extreme temperatures, their static nature fundamentally limits active and dynamic wave manipulation. In this work, we present, to our knowledge, the first demonstration of integrating superconducting niobium nitride (NbN) into phase-coding metamaterials, enabling highly efficient and dynamically reconfigurable and temperature-tunable beam-splitting devices. The proposed superconducting phase-coding design supports customizable patterns of more than 100 reflected beams across the entire temperature range, achieving a power efficiency of 91.1% within the 0.7–1.05 THz bandwidth. Furthermore, a novel superconducting-gold composite metamaterial further enables dynamic reconfiguration of beam number, transitioning between two-beam (room temperature) and four-beam (4.2 K) states. The device can also be implemented to achieve dual-polarized beam combining in the far field. Through rigorous characterization using a custom-built cryogenic THz far-field measurement system, two distinct beam-splitting devices are successfully validated. This work not only validates the outstanding dynamic tuning and multi-beam manipulation capabilities of superconducting coding metamaterials, but also introduces innovative solutions for THz systems under extreme cryogenic conditions—including deep-space exploration and quantum communications—through the development of novel amplitude-control materials.