Revealing the Hidden Plasmonic Modes of a Gold Nanocylinder

A metallic nanocylinder is one of the most studied simple plasmonic nanostructures. Due to its internal symmetry, it can sustain different modes, but the majority of the studies focus on the horizontal dipolar resonance. Studying the whole variety of the excited modes in an individual nanocylinder is crucial to the development of further applications. Herein, we analyze the modes excited in a single gold nanocylinder on a glass substrate with standard optical characterization techniques and numerical simulations. The analysis of the scattering radiation patterns of the different modes shows that specific collection geometries are required to distinguish them. We propose a new method to record the hidden modes using a conventional dark-field scattering microscope, and for the first time, we show how the optically. vertical dipolar mode of a single nanocylinder can be revealed optically.