Abstract
All-dielectric nanostructures have recently opened exciting opportunities for functional nanophotonics, owing to their strong optical resonances along with low material loss in the near-infrared range. Pushing these concepts to the visible range is hindered by their larger absorption coefficient, thus encouraging the search for alternative dielectrics for nanophotonics. Here, we employ bandgap engineering to synthesize hydrogenated amorphous Si nanoparticles (a-Si:H NPs) offering ideal features for functional nanophotonics. We observe significant material loss suppression in a-Si:H NPs in the visible range caused by hydrogenation-induced bandgap renormalization, producing strong higher-order resonant modes in single NPs with Q factors up to ~100 in the visible and near-IR range. We also realize highly tunable all-dielectric meta-atoms by coupling a-Si:H NPs to photochromic spiropyran molecules. ~70% reversible all-optical tuning of light scattering at the higher-order resonant mode under a low incident light intensity is demonstrated. Our results promote the development of high-efficiency visible nanophotonic devices.
Highlights
All-dielectric nanostructures have recently opened exciting opportunities for functional nanophotonics, owing to their strong optical resonances along with low material loss in the near-infrared range
By tuning the hydrogen concentration, amorphous Si nanoparticles (a-Si):H NPs can obtain the absorption bandgap larger than 1.77 eV (700 nm) via bandgap engineering, and sustain a lower loss and strong higherorder scattering modes with high Q factors in the visible range
Raman spectroscopy was employed to verify that the distortion of the Si–Si bond, and the amorphous nature of a-Si:H NPs increases with an increase of hydrogen concentration
Summary
All-dielectric nanostructures have recently opened exciting opportunities for functional nanophotonics, owing to their strong optical resonances along with low material loss in the near-infrared range. Crystalline silicon (c-Si) has a broad optical absorption in the wavelength range from 300 to 1150 nm, with an absorption coefficient larger than 1 × 103 cm−1 over the whole visible region[48] that reduces Q factor of the fundamental magnetic dipole (MD)[31] and suppresses all high-order modes. This obstacle has prevented the development of low-loss and compact photonic devices for the visible region, and prompts a further search for alternative materials. We employ bandgap engineering to tailor hydrogenated amorphous
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