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Sugimoto H, Hinamoto T, Kazuoka Y, Assadillayev A, Raza S, Fujii M. Mode Hybridization in Silicon Core-Gold Shell Nanosphere. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2204890. [PMID: 36156856 DOI: 10.1002/smll.202204890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 09/13/2022] [Indexed: 06/16/2023]
Abstract
A dielectric core-metal shell nanosphere has attracted scientific and technological interests due to the unique optical resonances arising from the hybridization of surface plasmon modes and cavity modes. The previous studies focus on a low-index dielectric core without its own optical resonances. Here, optical resonances of a core-shell nanosphere with a high refractive index (n ≈ 4) core with the lowest order Mie resonances in the visible range are investigated theoretically and experimentally. Scattering and absorption spectra of a core-shell nanosphere for different values of the core refractive index are first analyzed, and there is a transition of the hybridization scheme around n ≈ 2. Above the value, a characteristic hybridized mode with strong absorption and weak scattering emerges in the near-infrared range. A core-shell nanosphere composed of a silicon core and a gold shell is prepared, and the resonance modes are studied by single particle scattering spectroscopy and electron energy loss spectroscopy (EELS) in a transmission electron microscope. The core-shell nanospheres exhibit the hybridized modes depending on the core diameter. The hybridized mode as well as the higher order one that is not observable in the scattering spectroscopy is observed in the EELS.
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Affiliation(s)
- Hiroshi Sugimoto
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, Rokkodai, Nada, Kobe, 657-8501, Japan
| | - Tatsuki Hinamoto
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, Rokkodai, Nada, Kobe, 657-8501, Japan
| | - Yusuke Kazuoka
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, Rokkodai, Nada, Kobe, 657-8501, Japan
| | - Artyom Assadillayev
- Department of Physics, Technical University of Denmark, Fysikvej, Kongens Lyngby, DK-2800, Denmark
| | - Søren Raza
- Department of Physics, Technical University of Denmark, Fysikvej, Kongens Lyngby, DK-2800, Denmark
| | - Minoru Fujii
- Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, Rokkodai, Nada, Kobe, 657-8501, Japan
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Au@Ag Core-Shell Nanorods Support Plasmonic Fano Resonances. Sci Rep 2020; 10:5921. [PMID: 32246058 PMCID: PMC7125092 DOI: 10.1038/s41598-020-62852-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 03/20/2020] [Indexed: 11/09/2022] Open
Abstract
In this work, we investigated experimentally and theoretically the plasmonic Fano resonances (FRs) exhibited by core-shell nanorods composed of a gold core and a silver shell (Au@Ag NRs). The colloidal synthesis of these Au@Ag NRs produces nanostructures with rich plasmonic features, of which two different FRs are particularly interesting. The FR with spectral location at higher energies (3.7 eV) originates from the interaction between a plasmonic mode of the nanoparticle and the interband transitions of Au. In contrast, the tunable FR at lower energies (2.92-2.75 eV) is ascribed to the interaction between the dominant transversal LSPR mode of the Ag shell and the transversal plasmon mode of the Au@Ag nanostructure. The unique symmetrical morphology and FRs of these Au@Ag NRs make them promising candidates for plasmonic sensors and metamaterials components.
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Zhou J, Panday A, Xu Y, Chen X, Chen L, Ji C, Guo LJ. Visualizing Mie Resonances in Low-Index Dielectric Nanoparticles. PHYSICAL REVIEW LETTERS 2018; 120:253902. [PMID: 29979064 DOI: 10.1103/physrevlett.120.253902] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2017] [Indexed: 06/08/2023]
Abstract
Resonant light scattering by metallic and high-index dielectric nanoparticles has received enormous attention and found many great applications. However, low-index dielectric nanoparticles typically do not show resonant scattering behaviors due to poor light confinement caused by small index contrast. This Letter describes a simple and effective approach to drastically enhance the resonance effect of the low-index particles by partial metal dressing. Mie resonances of low-index nanoparticles can now be easily visualized by scattered light. This scattering peak depends on sphere size and has a reasonable linewidth. A size difference as small as 8 nm was resolved by a peak shift or even by color change. The scattering peak is attributed to the enhanced TE_{11} Mie resonance of the low-index nanospheres. The metal dress not only provides a high-reflection boundary, but also functions as an antenna to couple the confined light power to the far field, leading to scattering maxima in the spectra. Additionally, the enhanced TE_{11} Mie resonance in low-index nanoparticles features a considerable magnetic response due to the strong circulating displacement currents induced by the intensified E field despite of a low permittivity (hence low index) of the particles. The enhanced Mie resonances could be used to sense minute changes in size or refractive index of low-index nanoparticles and benefit a wide range of applications.
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Affiliation(s)
- Jing Zhou
- Department of Electrical Engineering and Computer Science, The University of Michigan, Ann Arbor, Michigan 48109, USA
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yutian Road, Shanghai 200083, China
| | - Ashwin Panday
- Macromolecular Science and Engineering, The University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Yuntao Xu
- Department of Electrical Engineering and Computer Science, The University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Xi Chen
- Applied Physics, The University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Long Chen
- Applied Physics, The University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Chengang Ji
- Department of Electrical Engineering and Computer Science, The University of Michigan, Ann Arbor, Michigan 48109, USA
| | - L Jay Guo
- Department of Electrical Engineering and Computer Science, The University of Michigan, Ann Arbor, Michigan 48109, USA
- Macromolecular Science and Engineering, The University of Michigan, Ann Arbor, Michigan 48109, USA
- Applied Physics, The University of Michigan, Ann Arbor, Michigan 48109, USA
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Li Z, Sun R, Zhang C, Wan M, Gu P, Shen Q, Chen Z, Wang Z. Boosting figures of merit of cavity plasmon resonance based refractive index sensing in dielectric-metal core-shell resonators. OPTICS EXPRESS 2016; 24:19895-19904. [PMID: 27557265 DOI: 10.1364/oe.24.019895] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We theoretically investigate the sensing performance of the dielectric-metal core-shell resonators (DMCSRs) that support multipolar sharp magnetic and electric-based cavity plasmon resonances. We show that at the cavity resonances the ability of the DMCSRs to strongly confine the optical fields inside the cavity is robust against the existence of nano-openings in the metal shell layer. As a result, both the perfect DMCSRs having a complete metal shell layer and the non-perfect DMCSRs with nano-openings in the metal shell layers exhibit high refractive index sensitivities of 700 ~1200 nm/RIU. Furthermore, we demonstrate that such high refractive index sensitivities could be well maintained in an array of interconnected non-perfect DMCSRs. The narrow linewidths of the cavity plasmon resonances coupled with their high index sensitivities make the array of non-perfect DMCSRs possess high figure of merit (FOM) values up to ~88, approaching the theoretically estimated upper limit (FOM ≈108) for gold standard prism coupled surface-plasmon sensors.
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Gu P, Wan M, Wu W, Chen Z, Wang Z. Excitation and tuning of Fano-like cavity plasmon resonances in dielectric-metal core-shell resonators. NANOSCALE 2016; 8:10358-10363. [PMID: 27139034 DOI: 10.1039/c5nr09249c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Fano resonances have been realized in plasmonic systems and have found intriguing applications, in which, however, precisely controlled symmetry breaking or particular arrangement of multiple constituents is usually involved. Although simple core-shell type architectures composed of a spherical dielectric core and a concentric metallic shell layer have been proposed as good candidates that support inherent Fano resonances, these theoretical predictions have rarely seen any detailed experimental investigation. Here, we report on the experimental investigation of the magnetic and electric-based multipolar plasmonic Fano resonances in the dielectric-metal core-shell resonators that are formed by wrapping a nearly perfect metal shell layer around a dielectric sphere. We demonstrate that these Fano resonances originate from the interference between the Mie cavity and sphere plasmon resonances. Moreover, we present that the variation on either the dielectric core size or core refractive index allows for easily tuning the observed Fano resonances over a wide spectral range. Our findings are supported by excellent agreement with analytical calculations, and offer unprecedented opportunities for realizing ultrasensitive bio-sensors, lasing and nonlinear optical devices.
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Affiliation(s)
- Ping Gu
- School of Physics and National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China.
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