Splitter of topological photonic waveguide in semiconductor platform

Abstract We propose a splitter that can separate a topological photonic waveguide into two branches with the desired relative wave intensity while keeping the waveguide mode intact. The device consists of semiconductor photonic crystals, topological insulators, and trivial insulators surrounding a rhombic patch X, with X varying from trivial to topological via a graphene-like semimetal, all formed by arranging nano airholes in patterns of C 6v symmetry. Patch X establishes an effective potential for the input topological wave function, guiding it to the two output ports in a tunnelling-like manner with the desired relative intensity. Our Si-photonics fabricated splitter achieves continuous power ratios between output ports from 10.22 dB to -9.17 dB. With a miniaturised size of ~ 10 µm, it surpasses conventional silicon-based Y-splitters. This breakthrough in controlling topological photonic waveguide splitting is vital for high-performance topological photonic integrated circuits (TPICs), opening up new possibilities for innovative functionality across diverse platforms.