Y-branch wavelength demultiplexer based on topological valley photonic crystals

Inspired by topological insulators in the condensed matter physics, topological photonics is a new paradigm, which is free of light backscattering at sharp waveguide bends due to the topological protection, and shows unidirectional light propagation based on the valley-chiral locking. Herein, we propose a two-channel Y-branch wavelength demultiplexer operating at the telecom band using the topological photonic integrated circuits for the first time. The proposed Y-branch wavelength demultiplexer is designed as adjoining and separating of two different topological interfaces at its input and output ports, respectively. Topological edge states with spectral interleaving can be excited in the two different topological interfaces, and be split into two output ports of the demultiplexer in short and long wavelengths. The Y-branch topological waveguide can be used as a dichroic mirror or a wavelength filter for separating light at two different wavelengths. The proposed topological integrated circuit is immune to structural defects. It is promising for the practical applications of optical interconnects and signal processing on a silicon photonic chip.