Ultrahigh Enhancement of Electromagnetic Fields by Exciting Localized with Extended Surface Plasmons

TL;DR

This paper demonstrates that exciting localized surface plasmons via extended surface plasmons using the Kretschmann-Raether configuration significantly amplifies electromagnetic fields, surpassing direct excitation methods, with implications for sensing and optoelectronics.

Contribution

It introduces a method to achieve ultrahigh electromagnetic field enhancement by utilizing extended surface plasmons to excite localized surface plasmons, outperforming traditional excitation techniques.

Findings

EM field enhancement is 1-3 orders higher with ESP excitation.

Maximum enhancement occurs at the ESP resonance angle.

Strong vertical confinement of ESPs leads to ultrahigh field intensities.

Abstract

Excitation of localized surface plasmons (LSPs) of metal nanoparticles (NPs) residing on a flat metal film has attracted great attentions recently due to the enhanced electromagnetic (EM) fields found to be higher than the case of NPs on a dielectric substrate. In the present work, it is shown that even much higher enhancement of EM fields is obtained by exciting the LSPs through extended surface plasmons (ESPs) generated at the metallic film surface using the Kretschmann-Raether configuration. We show that the largest EM field enhancement and the highest surface-enhanced fluorescence intensity are obtained when the incidence angle is the ESP resonance angle of the underlying metal film. The finite-difference time-domain simulations indicate that excitation of LSPs using ESPs can generate 1-3 orders higher EM field intensity than direct excitation of the LSPs using incidence from free space. The ultrahigh enhancement is attributed to the strong confinement of the ESP waves in the vertical direction. The drastically intensified EM fields are significant for highly-sensitive refractive index sensing, surface-enhanced spectroscopies, and enhancing the efficiency of optoelectronic devices.