Enhanced Electromagnetic Chirality by Locally Excited Surface Plasmon Polaritons

TL;DR

This paper demonstrates that surface plasmon polaritons excited by near-field sources can significantly enhance optical chirality in the UV spectrum, advancing chiral bio-sensing capabilities.

Contribution

It reveals that chiral excitation of SPPs can locally and globally enhance optical chirality, overcoming previous limitations of TM modes in plasmonic sensors.

Findings

SPPs excited by near-field sources exhibit rich chiral characteristics.

Chiral excitation of SPPs results in manifold enhancement of optical chirality.

Enhanced UV-range optical chirality improves chiral bio-sensing sensitivity.

Abstract

The possibility to enhance chiral light-matter interactions through plasmonic nanostructures provides entirely new opportunities for greatly improving the detection limits of chiroptical spectroscopies down to the single molecule level. The most pronounced of these chiral interactions occur in the ultraviolet (UV) range of the electromagnetic spectrum, which is difficult to access with conventional localized plasmon resonance based sensors. Although Surface Plasmon Polaritons (SPPs) on noble metal films can sustain resonances in the desired spectral range, their transverse magnetic nature has been an obstacle for enhancing chiroptical effects. Here we demonstrate, both analytically and numerically, that SPPs excited by near-field sources can exhibit rich and non-trivial chiral characteristics. In particular, we show that the excitation of SPPs by a chiral source not only results in a locally enhanced optical chirality but also achieves manifold enhancement of net optical chirality. Our finding that SPPs facilitate a plasmonic enhancement of optical chirality in the UV part of the spectrum is of great interest in chiral bio-sensing.