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<p>Using the finite difference time-domain (FDTD) numerical method, the present study deals with the spectral characteristics of a hybrid metal–insulator-metal (MIM) nanostructure consisting of an array of core–shell (aluminum-silver) nanocones separated by a thin dielectric layer from the aluminum metal layer. Calculations show that by choosing the appropriate thickness and refractive index of the dielectric layer in this nanostructure, a suitable and interesting optical response is obtained in three spectral regions: deep-UV, near-UV, and visible. The effects of the hybrid modes of nanocones (Al@Ag) and their coupling with the plasmonic modes of the substrate can create three modes at wavelengths of 145, 343, and 441&#xa0;nm. In addition to the coupling of hybrid plasmons, the magnetic resonances induced in the dielectric layer as well as the propagating plasmonic modes contribute to the increased coupling intensity of plasmonic modes. By changing the nanocone shell’s geometrical dimensions and the surrounding environment’s refractive index, one can see the created plasmonic modes with better spectral characteristics. The first mode at the wavelength of 145&#xa0;nm is formed under the plasmonic effects of the core, reducing the FWHM to 25&#xa0;nm with a sensitivity of 70&#xa0;nm/RIU. This mode makes it possible to reach the deep-UV spectral region with high sensitivity, and this feature has been rarely observed in other nanostructures. Increasing the thickness of the shell activates the modes created in the near-UV (359&#xa0;nm) and visible (475&#xa0;nm) regions, with a sensitivity of 70&#xa0;nm/RIU and 80&#xa0;nm/RIU, respectively. The results of this research can become the basis for designing new and more efficient nanostructures that are specifically used in optical sensors and other plasmonic devices.</p>

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Numerical Investigation of Plasmonic Hybrid Modes, Enhanced in Deep-UV–Visible Regions, in Metal-Dielectric-Metal (MIM) Nanostructures Based on Al@Ag Core–Shell Periodic Nanocones

  • 期刊论文

  • 发表日期：

    2025年1月6日

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  • Nasrin Sepahvand,
  • Abdol-Mohammad Ghalambor Dezfuli,
  • Mohsen Bahrami

摘要

Using the finite difference time-domain (FDTD) numerical method, the present study deals with the spectral characteristics of a hybrid metal–insulator-metal (MIM) nanostructure consisting of an array of core–shell (aluminum-silver) nanocones separated by a thin dielectric layer from the aluminum metal layer. Calculations show that by choosing the appropriate thickness and refractive index of the dielectric layer in this nanostructure, a suitable and interesting optical response is obtained in three spectral regions: deep-UV, near-UV, and visible. The effects of the hybrid modes of nanocones (Al@Ag) and their coupling with the plasmonic modes of the substrate can create three modes at wavelengths of 145, 343, and 441 nm. In addition to the coupling of hybrid plasmons, the magnetic resonances induced in the dielectric layer as well as the propagating plasmonic modes contribute to the increased coupling intensity of plasmonic modes. By changing the nanocone shell’s geometrical dimensions and the surrounding environment’s refractive index, one can see the created plasmonic modes with better spectral characteristics. The first mode at the wavelength of 145 nm is formed under the plasmonic effects of the core, reducing the FWHM to 25 nm with a sensitivity of 70 nm/RIU. This mode makes it possible to reach the deep-UV spectral region with high sensitivity, and this feature has been rarely observed in other nanostructures. Increasing the thickness of the shell activates the modes created in the near-UV (359 nm) and visible (475 nm) regions, with a sensitivity of 70 nm/RIU and 80 nm/RIU, respectively. The results of this research can become the basis for designing new and more efficient nanostructures that are specifically used in optical sensors and other plasmonic devices.