Electrically Tunable On‐Chip Topological Photonics with Integrated Carbon Nanotubes

Abstract Miniaturized high‐speed integrated terahertz (THz) circuits are crucial for enabling THz wireless communication, offering unprecedented data rates, ultra‐low latency, and enhanced capacity. Topological photonics provides a promising platform for the efficient operation and integration of THz wireless communication systems owing to its ability to robustly guide light within a compact device footprint. However, the absence of reconfigurable and compact on‐chip devices limits the potential of topological photonics for various functions, including dynamic spectrum modulation in THz communication systems. Here, electrically tunable on‐chip topological THz broadband modulator and narrowband filter are demonstrated by integrating 2D carbon nanotube (CNT) sheets with on‐chip THz valley‐Hall photonic crystals (VPCs). By applying a bias to the 2D CNT sheets to locally heat the topological chip, the waveguide achieves an average transmission modulation depth (MD) of 71% across a broad bandwidth of 33 GHz and reaches up to 90% MD at a single frequency. In addition, the CNT‐integrated waveguide‐cavity coupled system shows a 0.54 GHz resonance frequency shift while maintaining a high quality factor of the topological cavity resonance. The study merges THz topological photonics with 2D materials, opening new avenues for versatile applications in tunable THz topological photonic integrated circuits, including modulators, filters, and switches.