Accounting for inhomogeneous broadening in nano-optics by electromagnetic modeling based on Monte Carlo methods

Abstract

Many experimental systems consist of large ensembles of uncoupled or weakly interacting elements operating as a single whole; this is particularly the case for applications in nano-optics and plasmonics, including colloidal solutions, plasmonic or dielectric nanoparticles on a substrate, antenna arrays, and others. In such experiments, measurements of the optical spectra of ensembles will differ from measurements of the independent elements as a result of small variations from element to element (also known as polydispersity) even if these elements are designed to be identical. In particular, sharp spectral features arising from narrow-band resonances will tend to appear broader and can even be washed out completely. Here, we explore this effect of inhomogeneous broadening as it occurs in colloidal nanopolymers comprising selfassembled nanorod chains in solution. Using a technique combining finite-difference time-domain simulations and Monte Carlo sampling, we predict the inhomogeneously broadened optical spectra of these colloidal nanopolymers and observe significant qualitative differences compared with the unbroadened spectra. The approach combining an electromagnetic simulation technique with Monte Carlo sampling is widely applicable for quantifying the effects of inhomogeneous broadening in a variety of physical systems, including those with many degrees of freedom that are otherwise computationally intractable.photonics | FDTD | random sampling | stochastic

Coupling-Enhanced Broadband Mid-infrared Light Absorption in Graphene Plasmonic Nanostructures

“…35 Therefore, both red and blue shifts of the plasmonic resonance frequency and both enhancement and suppression of the resonance intensity were previously observed in coupled metal plasmonic nanostructures. [27][28][29][30][31][32] Furthermore, we confirm the validity of Eqs. ( 7) and ( 9) using experimental results.…”

“…This observation is different from that in coupled metallic nanoparticles, in which the coupling can lead to both red or blue shifts in resonance and the intensity can be suppressed or enhanced, depending on the excitation scheme, the periodicity of structures, the size of particles, etc. [27][28][29][30][31][32]…”

Dynamic single gold nanoparticle visualization by clinical intracoronary optical coherence tomography

“…This broadening of the extinction cross section spectra is attributed to the existence of GNRs of different sizes in the dispersion (polydispersity). As the morphology (size and aspect ratio) of GNRs determine the spectral location of their surface plasmon resonance wavelength, such polydispersity leads to an inhomogeneous line broadening in the extinction spectra . As a consequence of this spectral broadening, all GNPs present a non‐vanishing extinction cross section at the OCT wavelength (, see detailed values in Table ).…”

Reconciling measured scattering response of 3D metamaterials with simulation

“…While boutique fabrication approaches such as e-beam writing over small areas are inherently more immune to this variation, a technique such as MPL which can be used to create wafer-scale arrays of material is susceptible to dimensional shifts, or ensemble averages of structures rather than homogeneous arrays and hence changes in the electromagnetic behavior. Much like inhomogeneous broadening which affects the linewidth of quantum dot lasers, practical nano-photonic systems also must reconcile the inherent physical dimension variation present in fabrication of structures at these size scales [17], either through exacting fabrication tolerance and control or by design of electromagnetic solutions which are robust to such variation.…”