Wang Mingsong, Krasnok Alex, Lepeshov Sergey, Hu Guangwei, Jiang Taizhi, Fang Jie, Korgel Brian A, Alù Andrea, Zheng Yuebing
Walker Department of Mechanical Engineering and Texas Materials Institute, The University of Texas at Austin, Austin, TX, 78712, USA.
Photonics Initiative, Advanced Science Research Center, City University of New York, New York, NY, 10031, USA.
Nat Commun. 2020 Oct 7;11(1):5055. doi: 10.1038/s41467-020-18793-y.
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.
全介质纳米结构最近为功能性纳米光子学带来了令人兴奋的机遇，这得益于它们在近红外范围内的强光学共振以及低材料损耗。然而，将这些概念拓展到可见光范围却受到其较大吸收系数的阻碍，因此促使人们寻找用于纳米光子学的替代电介质。在此，我们采用带隙工程来合成氢化非晶硅纳米颗粒（a-Si:H NPs），其为功能性纳米光子学提供了理想特性。我们观察到，氢化诱导的带隙重整化导致a-Si:H NPs在可见光范围内的材料损耗显著抑制，从而在单个纳米颗粒中产生强高阶共振模式，在可见光和近红外范围内的品质因数高达~100。我们还通过将a-Si:H NPs与光致变色螺吡喃分子耦合，实现了高度可调谐的全介质元原子。在低入射光强度下，展示了在高阶共振模式下约70%的光散射可逆全光调谐。我们的结果推动了高效可见光纳米光子器件的发展。
