Coupled-Dipole Modeling and Experimental Characterization of Geometry-Dependent Trochoidal Dichroism in Nanorod Trimers

Abstract

Noble metal nanoparticles host surface plasmon resonances that confine electromagnetic waves below the diffraction limit of light, making them effective building blocks for near-field optical antennas. Efficient prediction and design of nanoantenna systems are facilitated by improved understanding of their optical properties. Here, we utilize an intuitive coupled-dipole model for fan-shaped gold nanorod trimers together with experiments to investigate the role of near-and far-field effects upon optical dichroism using both linear and trochoidal polarizations with cartwheeling field motion matching the geometry of the trimers. Our coupled-dipole model predicts the linear and trochoidal dichroism that we observe in experiments, and we demonstrate that trochoidal intensity modulation can be tuned and reversed by varying the geometric parameters of the gold nanorod trimers. Simple analytical models, coupled with easily understood visualizations, provide a useful framework for predictive nanoantenna design applications.

Optical Ultracompact Directional Antennas Based on a Dimer Nanorod Structure

“…Optical nanoantennas act as effective transducers between the near-and far-field regions of these nanoemitters, and as such they have been widely applied for manipulating the interaction between light and matter [6]. To date, several schemes have been used to engineer the emitter properties, including tuning excitation [7], decay rate [8], polarization [9], frequency conversion [10,11], spectral modulation [12], nonlinear processes [13] and emission direction [14,15]. The most commonly used design for directional emission is based on the Yagi-Uda geometry [14][15][16][17] inspired by radiofrequency devices.…”