Plasmonic Bi-Cavity Nanostructure for Efficient Light Collection and Localization
Abstract
Tip-enhanced Raman spectroscopy (TERS) typically relies on high-NA excitation to generate a strong axial field at the tip apex, which shortens the working distance and constrains sample geometries. We show that a plasmonic bi-cavity tip, the plasmon-tunable tip pyramid (PTTP), co-tuned in nanopyramid length L and plateau length W, supports a hybrid antenna-cavity mode that funnels energy to the apex under radially polarized, on-axis excitation, even with a dry objective of NA = 0.75. Finite-element simulations identify W as a design-critical parameter that sets an in-plane surface-plasmon-polariton (SPP) Fabry-P\'erot-like resonance; co-tuning (L,W) yields a periodic series of maximal apex |E|^2. Experiments on monolayer graphene confirm near-field enhancement and reproduce the characteristic annular TERS point spread function (PSF) with NA = 0.75. Relaxing the NA requirement increases working distance and compatibility with constrained environments, pointing to practical, deployment-ready nano-Raman instrumentation.
Keywords
Cite
@article{arxiv.2601.11870,
title = {Plasmonic Bi-Cavity Nanostructure for Efficient Light Collection and Localization},
author = {Vitor Monken and Raul Correa and Hudson Miranda and Cassiano Rabelo and Rafael Nadas and Thiago L. Vasconcelos and Luiz Gustavo Cancado and Ado Jorio},
journal= {arXiv preprint arXiv:2601.11870},
year = {2026}
}
Comments
6 pages, 5 figures, submitted to Analysis and Sensing