Mode Hybridization in Silicon Core-Gold Shell Nanosphere.

Area of Science:

• Plasmonics and Nanophotonics
• Materials Science

Background:

• Dielectric core-metal shell nanospheres exhibit unique optical resonances due to coupled surface plasmon and cavity modes.
• Previous research focused on low-index dielectric cores, limiting the exploration of diverse optical phenomena.

Purpose of the Study:

• To investigate optical resonances in core-shell nanospheres featuring high refractive index dielectric cores (n ≈ 4).
• To explore the hybridization of Mie resonances with plasmonic modes in silicon-gold core-shell nanostructures.

Main Methods:

• Theoretical analysis of scattering and absorption spectra for varying core refractive indices.
• Experimental fabrication of silicon-gold core-shell nanospheres.
• Characterization using single particle scattering spectroscopy and electron energy loss spectroscopy (EELS).

Main Results:

• A transition in hybridization schemes occurs around a core refractive index of n ≈ 2.
• A distinct hybridized mode with strong absorption and weak scattering emerges in the near-infrared range for high-index cores.
• Hybridized and higher-order modes were observed, with EELS revealing modes not seen in scattering spectroscopy.

Conclusions:

• High refractive index dielectric cores enable novel hybridized optical resonances in core-shell nanostructures.
• The core diameter influences the observed hybridized modes.
• EELS provides complementary insights into the optical resonances of these nanostructures.