When two valley edge states (VESs) in an A-B-A structure approach each other, mutual interference inevitably arises. However, in most cases, the degree of interference at a given frequency remains fixed, lacking an effective strategy for continuous tuning of the coupling strength. In this article, we present a coupled topological waveguide in which one channel incorporates the phase-change material ${\mathrm{Sb}}_2{\mathrm{S}}_3$. By adjusting the refractive index of ${\mathrm{Sb}}_2{\mathrm{S}}_3$, the wave vector of the corresponding VES can be flexibly tuned. Since mode coupling is governed by the wave-vector matching condition, this tunability allows precise control of the coupling coefficient between the two VESs at a specific frequency, thereby enabling dynamically reconfigurable beam-splitting behavior. Furthermore, with a large wave-vector mismatch, we achieve fully decoupled transmission, where the VESs propagate along their respective channels with minimal crosstalk, even in closely spaced waveguides. This capability for controllable interference and low-crosstalk propagation provides a promising route for the realization of high-density, multichannel photonic integration.

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• Photonic crystal waveguide
• Topological effects in photonic systems