Topological Landau–Zener nanophotonic circuits

Abstract

.Topological edge states (TESs), arising from topologically nontrivial phases, provide a powerful toolkit for the architecture design of photonic integrated circuits, since they are highly robust and strongly localized at the boundaries of topological insulators. It is highly desirable to be able to control TES transport in photonic implementations. Enhancing the coupling between the TESs in a finite-size optical lattice is capable of exchanging light energy between the boundaries of a topological lattice, hence facilitating the flexible control of TES transport. However, existing strategies have paid little attention to enhancing the coupling effects between the TESs through the finite-size effect. Here, we establish a bridge linking the interaction between the TESs in a finite-size optical lattice using the Landau–Zener model so as to provide an alternative way to modulate/control the transport of topological modes. We experimentally demonstrate an edge-to-edge topological transport with high efficiency at telecommunication wavelengths in silicon waveguide lattices. Our results may power up various potential applications for integrated topological photonics.

Robust optical mode converter based on topological waveguide arrays

“…This is because, the finite size effect weakens the topological protection, resulting in band degeneracy breaking and the coupling between the TESs. [39] Considering the opposite phase distributions between the two TESs [Figs. 2(c) and 2(d)], the coupling between TESs will result in directional coupling between the two edge waveguides.…”

“…It is worth noticing that the field intensity distributions of TESs are asymmetric because the coupling strengths between the waveguides in topological mode converter are weaker than those in topological directional coupler. [38,39] As described in Subsection 2.3, the optical field that is localized at a single boundary of the waveguide arrays can be regarded as a linear superposition of the two TESs. However, unlike the design of the topological directional coupler mentioned in Subsection 2.3, the waveguides in the current waveguide arrays with larger widths support the TE 1 mode.…”