Rigorous and extremely fast electromagnetic methods for diffraction problems

There is a growing demand for and lack of ultrafast, memory sparing but rigorous light scattering calculation techniques at large planar 2D diffracting objects. Examples include diffraction in OPC and in real-time scatterometry. Our approach to these requirements is the Generalized Source Method (GSM) formulated in Fourier space and its ongoing improvement. In this conference contribution, we report on recent success by switching from CPU to GPU computations and by application of the scattering-vector (S-vector) algorithm

Rigorous and extremely fast electromagnetic methods for diffraction problems

There is a growing demand for and lack of ultrafast, memory sparing but rigorous light scattering calculation techniques at large planar 2D diffracting objects. Examples include diffraction in OPC and in real-time scatterometry.Our approach to these requirements is the Generalized Source Method (GSM) formulated in Fourier space and its ongoing improvement. In this conference contribution, we report on recent success by switching from CPU to GPU computations and by application of the scattering-vector (S-vector) algorithm

Coupled Mode Modeling To Interpret Hybrid Modes and Fano Resonances in Plasmonic Systems

By generalizing the concept of extinction cross-section to complex valued extinction cross-section we analyze the coupling between plasmon modes in metallic dimers or quadrumers. Identifying the phase information in the field scattered by subsets of the whole plasmonic system allows to infer the formation of subradiant or super-radiant hybrid modes. We also propose a phenomenological modeling based on the use of coupled mode equations to deduce from rigorous calculations a quantitative estimate of mutual coupling coefficients when only two modes interfere. These coefficients determine the spectral position of hybrid modes. This approach is applied to two interacting silver spheres; the parameters of the energetic diagram are calculated as a function of the gap between spheres. In the case of two identical spheres illuminated with a linearly polarized light parallel or perpendicular to the dimer, only one hybrid mode is excited. The phenomenological modeling is then applied to a four-particle system, where the interaction between the initial dipolar modes gives rise to Fano resonances. In a weak coupling regime of the system, the asymmetric line profile in the extinction spectra of the system emerges from the superposition of a broad super-radiant mode and a sharp subradiant mode. A strong coupling regime is characterized by a broadened subradiant mode and a larger Fano resonance. The sharpness of the Fano resonance in the weak coupling regime makes this structure well suited for sensing applications

Fano-like resonance emerging from magnetic and electric plasmon mode coupling in small arrays of gold particles

In this work we theoretically and experimentally analyze the resonant behavior of individual 3 × 3 gold particle oligomers illuminated under normal and oblique incidence. While this structure hosts both dipolar and quadrupolar electric and magnetic delocalized modes, only dipolar electric and quadrupolar magnetic modes remain at normal incidence. These modes couple into a strongly asymmetric spectral response typical of a Fano-like resonance. In the basis of the coupled mode theory, an analytical representation of the optical extinction in terms of singular functions is used to identify the hybrid modes emerging from the electric and magnetic mode coupling and to interpret the asymmetric line profiles. Especially, we demonstrate that the characteristic Fano line shape results from the spectral interference of a broad hybrid mode with a sharp one. This structure presents a special feature in which the electric field intensity is confined on different lines of the oligomer depending on the illumination wavelength relative to the Fano dip. This Fano-type resonance is experimentally observed performing extinction cross section measurements on arrays of gold nano-disks. The vanishing of the Fano dip when increasing the incidence angle is also experimentally observed in accordance with numerical simulations

Fano-like resonance emerging from magnetic and electric plasmon mode coupling in small arrays of gold particles.

In this work we theoretically and experimentally analyze the resonant behavior of individual 3 × 3 gold particle oligomers illuminated under normal and oblique incidence. While this structure hosts both dipolar and quadrupolar electric and magnetic delocalized modes, only dipolar electric and quadrupolar magnetic modes remain at normal incidence. These modes couple into a strongly asymmetric spectral response typical of a Fano-like resonance. In the basis of the coupled mode theory, an analytical representation of the optical extinction in terms of singular functions is used to identify the hybrid modes emerging from the electric and magnetic mode coupling and to interpret the asymmetric line profiles. Especially, we demonstrate that the characteristic Fano line shape results from the spectral interference of a broad hybrid mode with a sharp one. This structure presents a special feature in which the electric field intensity is confined on different lines of the oligomer depending on the illumination wavelength relative to the Fano dip. This Fano-type resonance is experimentally observed performing extinction cross section measurements on arrays of gold nano-disks. The vanishing of the Fano dip when increasing the incidence angle is also experimentally observed in accordance with numerical simulations