Valley-Dependent Topological Photonic Crystals With Heterogeneous Bearded Interfaces for SOI-Based Integrated Optical Devices

Abstract

Topologically protected photonic edge states allow backscattering-free and disorder-immune light propagations, offering a new scheme for the development of on-chip information systems. Valley degree of freedom is one of the most reliable way to achieve topologically non-trivial states. Here, we take advantage of heterogeneous topological interfaces to construct integrated optical devices in the valley-dependent photonic crystals. Localized Berry curvature around the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</i> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K′</i> point guarantees the existence of valley kink states at telecom wavelengths below the light cone, ensuring both optical robustness and light confinement. We harness the combination of two kinds of bearded interfaces to realize wavelength-selective topological routing of light in the micro-ring resonators. The proposed bearded interfaces can support edge modes with large group indices up to 90, showing a great potential to obtain remarkable slow light effects. This work paves the way to implement optical buffers and reconfigurable photonic devices with the adoption of photonic valley pseudospin.