All-optical operation holds promise as the future of computing technology, and key components will include miniaturized waveguides (WGs) and optical switches that control narrow bandwidths. Nanowires (NWs) offer an ideal platform for nanoscale WGs, but their utility has been limited by the lack of comprehensive coupling scheme and of band selectivity. Here, we introduce a NW geometric superlattice (GSL) that allows controlled, narrow-band guiding in Si NWs through direct coupling of a Mie resonance with a bound guided state (BGS). Periodic diameter modulation in a GSL creates a Mie-BGS coupled-excitation that manifests as a scattering dark state with a pronounced scattering dip in the Mie resonance envelope. The frequency of the coupled mode, tunable from the visible to near-infrared, is determined by the pitch of the GSL and exhibits a Fourier-transform limited bandwidth. Using a combined GSL-WG system, we demonstrate spectrally-selective guiding and optical switching at telecommunication wavelengths, highlighting the potential to use NW GSLs for the design of on-chip optical components.

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Seokhyoung Kim, Kyoung-Ho Kim, David J. Hill, Hong-Gyu Park, and James F. Cahoon, "Mie-coupled bound guided states in nanowire geometric superlattices (Conference Presentation)," Proc. SPIE 10719, Metamaterials, Metadevices, and Metasystems 2018, 107191W (Presented at SPIE Nanoscience + Engineering: August 22, 2018; Published: 21 September 2018); https://doi.org/10.1117/12.2318028.5838246189001.