Active Ultrahigh‐<i>Q</i> (0.2 × 10⁶) THz Topological Cavities on a Chip

<jats:title>Abstract</jats:title><jats:p>Rapid scaling of semiconductor devices has led to an increase in the number of processor cores and integrated functionalities onto a single chip to support the growing demands of high‐speed and large‐volume consumer electronics. To meet this burgeoning demand, an improved interconnect capacity in terms of bandwidth density and active tunability is required for enhanced throughput and energy efficiency. Low‐loss terahertz silicon interconnects with larger bandwidth offer a solution for the existing inter‐/intrachip bandwidth density and energy‐efficiency bottleneck. Here, a low‐loss terahertz topological interconnect–cavity system is presented that can actively route signals through sharp bends, by critically coupling to a topological cavity with an ultrahigh‐quality (<jats:italic>Q</jats:italic>) factor of 0.2 × 10<jats:sup>6</jats:sup>. The topologically protected large <jats:italic>Q</jats:italic> factor cavity enables energy‐efficient optical control showing 60 dB modulation. Dynamic control is further demonstrated of the critical coupling between the topological interconnect–cavity for on‐chip active tailoring of the cavity resonance linewidth, frequency, and modulation through complete suppression of the back reflection. The silicon topological cavity is complementary metal–oxide–semiconductor (CMOS)‐compatible and highly desirable for hybrid electronic–photonic technologies for sixth (6G) generation terahertz communication devices. Ultrahigh‐<jats:italic>Q</jats:italic> cavity also paves the path for designing ultrasensitive topological sensors, terahertz topological integrated circuits, and nonlinear topological photonic devices.</jats:p>