On the limits of quasi-static theory in plasmonic nanostructures

Abstract

The approximated analytical approach of Quasi-Static Theory (QST) is widely used in modelling the optical response of plasmonic nanoparticles. It is well known that its accuracy is remarkable provided that the particle is much smaller than the wavelength of the interacting radiation and that the field induced inside the structure is approximately uniform. Here, we investigate the limits of QST range of validity for gold nanostructures freestanding in air. First, we compare QST predictions of scattering spectra of nanospheres and cylindrical nanowires of various sizes with the exact results provided by Mie scattering theory. We observe a non-monotonic behaviour of the error of QST as a function of the characteristic length of the nanostructures, revealing a non-trivial scaling of its accuracy with the scatterer size. Second, we study nanowires with elliptical section upon different excitation conditions by performing finite element numerical analysis. Comparing simulation results with QST estimates of the extinction cross-section, we find that QST accuracy is strongly dependent on the excitation conditions, yielding good results even if the field is highly inhomogeneous inside the structure.

Chemically-Controlled Ultrafast Photothermal Response in Plasmonic Nanostructured Assemblies

“…Therefore, in our simulations we consider p -polarized plane waves. Of course, the polarizability and extinction cross-section of nanowires scale differently to those of nanospheres (see, e.g., ref ( 51 ) and references therein). However, for p -polarized light, the 2D model is capable of capturing the qualitative behavior in terms of the linear and nonlinear response of the plasmonic resonance of Au NC assemblies, 39 yet keeping the numerical analysis relatively agile.…”

Numerical Study of the Optical Response of ITO-In2O3 Core-Shell Nanocrystals for Multispectral Electromagnetic Shielding

“…Several models have been developed to quantitatively describe the resonant behavior of NC (radii from 5 nm to 50 nm), through lumped-impedance representation based on the quasi-static approximation [24], [25]. The latter holds, depending on the scatterer size, the radiation wavelength and the field homogeneity in the nanoparticle [26]. The classic circuit concept, which is limited to the fundamental dipole mode, could be extended to predict the optical spectrum of nanoparticles independently on wavelength, size and material properties constraints [27].…”