Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 1709.08799

Collective Resonances in Nanoparticle Oligomers

Ben Hopkins
View original source ↗Read source document ↗Export metadata ↓

Abstract

The study of nanostructured artificial media for optics has expanded rapidly over the last few decades, coupled with improvements of fabrication technology that have enabled investigation of previously unrealisable optical scattering systems. Such development is complemented by renewed impetus to understand the physics of optical scattering from complex subwavelength geometry and nanoparticle systems. Here I investigate specifically the optical properties of closely packed arrangements of nanoparticles, known as nanoparticle oligomers, which provide an intuitive platform for analytical and numerical study on the formation and interplay of collective resonances. I consider both plasmonic nanoparticles, and also high-refractive-index dielectric nanoparticles that support Mie-type electric and magnetic dipole resonances. Specific outcomes of this study are listed as follows. (i) A new model is presented for optical Fano resonances, which is based on interference between nonorthogonal eigenmodes of the associated scattering object. This is demonstrated to correctly describe Fano resonances in both plasmonic and high-refractive-index dielectric nanoparticle oligomers. (ii) Polarisation-independent scattering and absorption losses are shown to be enforced by n-fold discrete rotational symmetry, Cn (n \geq 3), and the reciprocal degeneracy of eigenmodes. (iii) A form of circular dichroism that emerges from interaction of nonorthogonal resonances is presented, and specifically impacts the ratio of radiative scattering loss to dissipative absorption loss experienced by reciprocal plane waves. The sequence of general theoretical conclusions (i)-(iii) serve to build the understanding of optical scattering from nanoparticle systems while removing existing ambiguities.

Explore related subjects

physics.optics

Keep this discovery

BibTeXRIS

Ben Hopkins. 2017-09-26. Collective Resonances in Nanoparticle Oligomers. https://arxiv.org/abs/1709.08799

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Two-step high-accuracy microwave frequency measurement and time-frequency analysis based on optical frequency combs

Broadband microwave frequency measurement and time-frequency analysis are crucial for applications such as electronic warfare. However, when it comes to ultra wideband signal analysis, traditional electronic methods have high analysis accuracy, but intrinsic electronic bottlenecks limit their real-time analysis. Here, we propose and experimentally demonstrate a two-step microwave frequency measurement and time-frequency analysis method based on optical frequency combs. The system first performs coarse frequency localization over the 0-40 GHz range using stimulated-Brillouin-scattering-assisted frequency-to-time mapping (FTTM) and dual-comb channelized reception. The dual-comb is then reapplied for downconverting the signal under test, followed by digital signal processing to achieve high-accuracy unambiguous frequency extraction. Experimental results show that the system achieves mean single-tone frequency measurement errors of less than 10 kHz over 0-40 GHz. We further experimentally measure multi-tone, linearly frequency-modulated, and V-shaped frequency-modulated signals, demonstrating the proposed method's capability for analyzing complex signals.

physics.optics↗
arXiv2026

A Two-Mirror Faceted Projection System for EUV Lithography

We propose an all-reflective two-mirror projection system for extreme ultraviolet (EUV) lithography operating at exposure wavelengths of $13.5$~nm (Mo/Si) and $11.2$~nm (Ru/Be), delivering a fourfold ($4\times$) demagnification of the periodic mask pattern at a numerical aperture approaching unity ($\mathrm{NA}_{\max} \approx 0.993$). In contrast to conventional EUV projection objectives that incorporate 6--10 aspheric mirrors with an overall optical throughput of less than $15\%$, the proposed design redirects each accepted discrete spatial diffraction order scattered by the mask onto the wafer via a dedicated pair of planar mirror facets. The number of reflections is strictly fixed at two for all accepted orders, retaining $50$--$60\%$ of the power leaving the mask in each accepted order. We derive a spatial geometry providing rigorous optical path length equalization across all diffraction orders, thereby removing order-dependent propagation phase shifts. Individually optimized 30-bilayer Bragg multilayer coatings are designed for each facet using the transfer matrix method combined with global evolutionary optimization algorithms. The architecture is generalized to a three-dimensional vector formulation with a two-dimensionally periodic mask. Utilizing inverse lithography technology, Fourier parameterization, and a differentiable electromagnetic modal waveguide solver, we solve the synthesis problem for binary absorber masks (La absorber on a Ru/Be/Sr multilayer mirror). We demonstrate simulated aerial images of sub-10-nm features on the wafer (isolated peaks with a full width at half maximum (FWHM) of approximately $5.4$~nm and line pairs with a critical dimension of $6$~nm) and find that the two peaks remain resolved for the tested wafer defocus values from $0$ to $5$~nm along the $z$-axis.

physics.optics↗
arXiv2026

Antimony for broadband nanophotonics across the ultraviolet, visible and infrared

Semimetal elemental antimony (Sb) nanostructures show great potential for applications where nanophotonic properties play a key role, such as phase-change optical memories, non-linear optical elements, photothermal therapy agents, photodetectors and photocatalysts. However, designing advanced Sb-based photonic devices critically requires an accurate and reliable knowledge of the optical response of bulk and nanoscale Sb. Herein, we report for the first time a fully consistent and accurately measured dielectric function for Sb nanoscale films in a wide spectral range from the ultraviolet to the far infrared (4 - 0.04 eV, i.e. ~ 0.3 - 30 $\mu$m), surpassing previous reports that explored a limited spectral range. It is found that the Sb spectral response is driven exclusively by giant interband transitions in the visible up to mid infrared (4 - 0.4 eV, i.e. ~ 0.3 - 3 $\mu$m), and that their contribution dominates over that of free carriers down to 0.12 eV (i.e. ~ 10 $\mu$m). Such spectral response enables Sb nanostructures to display spectrally selective and tunable nanophotonic resonances. First, we showcase interband plasmonic resonances in the visible-to-near infrared for Sb nanogratings. Second, we report giant refractive index dielectric resonances in the mid infrared for nanostructured Sb/dielectric/metal resonant cavities. These findings open a pathway to optimized planar Sb nanoscale designs enabling a tailored light-matter interaction, which will be useful for integrated data, telecom, medical, optoelectronic and energy conversion devices operating in a broad spectral range.

physics.optics↗