Topological Landau–Zener nanophotonic circuits

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.

Broadband achromatic polarization insensitive metalens over 950 nm bandwidth in the visible and near-infrared

Metalenses are expected to play an increasingly important role in miniaturized and integrated optical imaging components/systems.However,devising broadband achromatic metalenses with high focusing efficiencies is still quite challenging.In this work,we proposed an aperture-shared partition phase cooperative manipulation approach for designing a highefficiency broadband achromatic metalens composed of two concentric sub-metalenses.As a proof-of-concept,an achromatic polarization-independent metalens is successfully designed for the visible and near-infrared range from450 nm to 1400 nm with the focusing efficiency over 70% for the wavelength range of 600 nm to 1400 nm.The approach reported here provides a possibility for designing a high-performance metalens,which has great potential applications in integrated optics.

Ultra-low-loss on-chip zero-index materials

Light travels in a zero-index medium without accumulating a spatial phase,resulting in perfect spatial coherence.Such coherence brings several potential applications,including arbitrarily shaped waveguides,phase-mismatch-free nonlinear propagation,large-area single-mode lasers,and extended superradiance.A promising platform to achieve these applications is an integrated Dirac-cone material that features an impedance-matched zero index.Although an integrated Dirac-cone material eliminates ohmic losses via its purely dielectric structure,it still entails out-of-plane radiation loss,limiting its applications to a small scale.We design an ultra-low-loss integrated Dirac cone material by achieving destructive interference above and below the material.The material consists of a square array of low-aspectratio silicon pillars embedded in silicon dioxide,featuring easy fabrication using a standard planar process.This design paves the way for leveraging the perfect spatial coherence of large-area zero-index materials in linear,nonlinear,and quantum optics.