Interface Manipulation Enables Widely Tunable Topological Outputs in Valley‐Photonic Frequency Multiplexers

Valley photonic crystals provide a robust platform for electromagnetic transport, yet conventional zigzag interfaces are constrained byfixed, narrow output geometry and limited tunability in integrated photonic circuits. Here, we reveal the distinct interface‐sliding sensitivities between AB and ACB heterostructures, where the former edge state exhibits strongly sliding‐dependent behavior while the latter supports robust large‐area output modes. Our innovation originates from the synergistic functional integration of two heterostructures with drastically contrasting sliding‐sensitivity properties for frequency multiplexing applications. Leveraging this difference, we strategically design a topological frequency‐division multiplexer with a wide range and a flexibly tunable output‐mode width by integrating these two hetero‐structures. The AB channels enable automatic frequency routing via precise glide modulation of the zigzag interface, which experimentally realizes frequency selectivity. The ACB hetero‐structure is embedded as the output channel to convert narrow boundary modes into large‐area transmission, with output width flexibly controlled by the number of middle C‐domain layers, independent of interface sliding. Through near‐field scanning experiments, we validate stable frequency multiplexing and robust transport with continuous output‐width tunability. This work establishes interface‐sliding sensitivity as a new design degree of freedom for topological photonic devices, offering an automatic and reconfigurable frequency‐division multiplexer solution for photonic integration and optical communication systems.