Journal Article terahertz topological photonic integrated circuits THz topological photonic integrated circuits topological cavity topological waveguides Active on‐chip terahertz Mach‐Zehnder Interferometer Phase control Silicon photonics THz on‐chip cavity THz on‐chip photonics Topological waveguides active non‐reciprocity berry curvature demultiplexer heterogeneous interfaces interface topology engineering inversion‐symmetric multiplexer non‐reciprocal critical coupling state on‐chip integrated isolator on‐chip terahertz interconnects on‐chip terahertz topological Mach‐Zehnder Interferometer on‐chip topological cavity optothermal control photonic crystals photonic filter photonic topological insulators radiation loss silicon THz interconnect silicon photonics