Spectrally Sharp Plasmon Resonances in the Near Infrared: Subwavelength Core-shell Nanoparticles

Abstract

Subwavelength plasmonic nanostructures have demonstrated many interesting phenomena and applications in recent decades. However, plasmonic resonance and associated properties, such as strong field enhancement, are limited to the visible regime due to the quasistatic nature of subwavelength plasmonic nanoparticles. Here, we numerically demonstrate spectral resonance tuning of subwavelength nanoparticles with a high-index core and a plasmonic shell while maintaining a sharp spectral peak. These core-shell-based nanoparticles have predominantly nonradiative loss and strong near-field enhancement due to their subwavelength feature size. This scheme can be further extended for magnetic and chiral meta-atoms. We suggest that these features of subwavelength core-shell-based nanoparticles are advantageous for many interesting applications including photothermal devices, enhanced light-matter interaction, and photonic circuitry.