Geometric effects on far-field coupling between multipoles of nanoparticles in square arrays

Abstract

Metallic nanoparticles organized in regular arrays exhibit an extraordinary spectral feature that arises from electromagnetic coupling between localized surface plasmons and constructive interference from diffracted far-field radiation. A rapid semianalytical description of coupling between dipoles and scattering modes is applied to examine the influence of nanoparticle size, dielectric, and interparticle separation on the occurrence, resonant wavelength, and intensity of the extraordinary spectral feature. Introducing a dynamic polarizability that includes higher-order electric poles into the description accurately characterizes plasmon resonances of larger particles. Previously unrecognized patterns and periodic variations in the extraordinary feature were observed to result from modulations in polarizability, as well as from interference of scattered modes that were distinguishable for the first time using the rapid semianalytic solution. Streamlined rational design of metamaterials with optimum optical properties using the rapid semianalytic coupled dipole approximation is considered.

Coupled dipole plasmonics of nanoantennas in discontinuous, complex dielectric environments

“…4 inset expands the spectra from 620 to 680 nm to show consistency between constructively interfering diffractive phase overlaps calculated with each polarizability. The aggregate dipolar lattice plasmon resonance (rightmost black circle in main figure) is blue-shifted from the single particle LSPR wavelength, consistent with previous results [21,40]. Close correspondence between analytic Mie and DDA-calculated polarizability spectra inserted into the rsa-CDA support multi-scale DDA/rsa-CDA application.…”

“…An analytical α is available for symmetric shapes such as spheres, spheroids, and toroids [35,40,41] in homogenous media, but external numerical calculation (e.g., DDA) is required for complex shapes [42] or most cases of non-uniform media. Polarizability corrections exist for spherical nanoantenna within non-lossy, multi-layered media [43], however they are not extendable to arbitrary antenna shapes or lossy substrates.…”

“…The rsa-CDA [20,38,40] reduced computational time by taking advantage of π/2 rotational symmetry in square lattices [40]. Dielectric data for Au reported by Johnson and Christy was used in all simulations [51].…”

Electron optics of nanoplasmonic metamaterials in bio/opto theranostics

“…6 Exact solutions of governing expressions grow difficult as descriptive detail increases for real environments. Finite difference and finite element methods can provide accurate approximations, but often at significant computational cost and reduced intuition regarding parametric significance.…”

Polarizability extraction for rapid computation of Fano resonance in nanoring lattices

“…Approximate coupled dipole solutions (CDA) to Maxwell's equations support rapid parametric analysis and optimization of Fano resonance 1 in nanosphere lattices by analytically prescribing particle polarizability in response to incident electromagnetism. [2][3][4] Ring structures are favorable to spheres in some applications, particularly biosensors, due to enhanced resonance in the infrared spectrum and higher local dielectric sensitivity. [5][6][7] Nanorings require higher order numerical methods, such as finite difference time domain (FDTD) 8 and boundary element method (BEM), 5 for parametric evaluation due to the lack of an analytical polarizability function.…”