Quantitative Benchmarking of Remote Excitation in Plasmonic Sensing with Enhanced Signal-to-Noise Ratio

TL;DR

This paper provides a quantitative comparison of remote and direct excitation in plasmonic SERS, showing that remote excitation offers a 30% improvement in SNR due to lower heating, with both schemes limited by electric-field effects.

Contribution

It introduces a systematic benchmarking framework for remote versus direct excitation in plasmonic sensing, revealing electric-field limits and the impact of heating on SNR.

Findings

Remote and direct SERS share a common electric-field limit.

Remote excitation reduces heating and enhances SNR by ~30%.

Spectral evolution is driven by local electric fields, not heating.

Abstract

Remote excitation using guided optical modes -- such as waveguides, fibers, or surface waves -- offers a promising alternative to direct optical excitation for surface-enhanced Raman scattering (SERS), particularly in applications requiring reduced heating, minimal invasiveness, and on-chip integration. However, despite its widespread use, systematic comparisons between remote and direct excitation remain limited. Here, we quantitatively benchmark both schemes by measuring power-dependent SERS responses from individual plasmonic nanogaps. We statistically analyze the maximum achievable SERS intensity before structural degradation, extract local temperatures, and evaluate signal-to-noise ratios (SNR). Our findings reveal that both remote and direct SERS share a common electric-field limit, despite exhibiting different levels of heating. This suggests that spectral evolution is primarily governed by the local electric field, which drives nanoscale atomic migration rather than excessive heating. Nonetheless, the lower heating associated with remote excitation enhances the Raman SNR by approximately 30%, improving measurement quality without compromising signal strength. This study establishes a quantitative framework for evaluating excitation strategies in plasmonic sensing, and challenges common assumptions about the role of heating in nanostructural stability under strong optical excitation.