Selection Rules for Structured Light in Nanooligomers and Other Nanosystems

Reich, Stéphanie; Mueller, Niclas S.; Bubula, Michal

doi:10.1021/acsphotonics.0c00359

Cited by 28 publications

(18 citation statements)

References 87 publications

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“…Therefore, HE 11 mode in a nanowire monomer is somewhat analogous to a resonant dipole excitation in a nanoparticle. Nanoparticle dimer and tetramer geometries have the symmetry point group D 2h and D 4h , respectively, yielding (in-plane) dipole-excitation-based symmetry-adapted eigenmodes as follows: four non-degenerate hybridized modes in the dimer and two doubly-degenerate and four non-degenerate hybridized modes in the tetramer [10]. Indeed, we observe similar HE 11 -mode-based hybridized waveguide modes in our nanowire dimers and tetramers.…”

Section: Resultssupporting

confidence: 59%

“…We choose to focus on nanowire dimers and tetramers specifically. The oligomer waveguide modes can be understood to arise due to the overlapping and interaction of monomer modes in the individual nanowires, somewhat analogous to the hybridization model for resonant excitations in nanoparticle oligomers [10]. To the best of our knowledge, the modal properties of nanowire oligomer waveguide modes have not been previously reported or their hybridization origin discussed, at least beyond recognizing coupled HE 11 modes leading to birefringence in nanowire dimers [11,12].…”

Section: Introductionmentioning

confidence: 93%

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Nanowire Oligomer Waveguide Modes towards Reduced Lasing Threshold

2020

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Semiconductor nanowires offer a promising route of realizing nanolasers for the next generation of chip-scale optoelectronics and photonics applications. Established fabrication methods can produce vertical semiconductor nanowires which can themselves act both as a gain medium and as a Fabry–Pérot cavity for feedback. The lasing threshold in such nanowire lasers is affected by the modal confinement factor and end facet reflectivities, of which the substrate end reflectivity tends to be limited due to small refractive index contrast between the nanowire and substrate. These modal properties, however, also depend strongly on the modal field profiles. In this work, we use numerical simulations to investigate waveguide modes in vertical nanowire oligomers (that is, arrangements of few vertical nanowires close to each other) and their modal properties compared to single nanowire monomers. We solve for the oligomer waveguide eigenmodes which are understood as arising from interaction of monomer modes and further compute the reflectivity of these modes at the end facets of the nanowires. We consider either the nanowires or an additional coating layer as the gain medium. We show that both types of oligomers can exhibit modes with modal properties leading to reduced lasing threshold and also give directions for further research on the topic.

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Section: Resultssupporting

confidence: 59%

Section: Introductionmentioning

confidence: 93%

Nanowire Oligomer Waveguide Modes towards Reduced Lasing Threshold

2020

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“…[ 59,60 ] They are optically inactive within the quasi‐static approximation but can be excited due to field retardation, by misalignment of Gaussian beams and by structured light. [ 50,51,60,61 ] Dark modes have smaller line width by approximately a factor of two, [ 51 ] which would bring the expected width of the SERS resonances much closer to the experimental values, Figure 3. This suggestion, however, has to explain why the SERS process is dominated by dark modes at the expense of the bright plasmons.…”

Section: Plasmonic Resonances In Sersmentioning

confidence: 74%

“…The decay is typically dominated by radiative damping. There are ways to excite dipole‐inactive modes in plasmonic structures through field retardation and tailored light‐fields, [ 50,51 ] but here, we focus on linearly polarized light and plasmonic structures that may be described within the quasi‐static approximation. The plasmon resonance with a width of several 100 meV leads to a predicted EM enhancement with a FWHM of ≈300 meV for many gold nanostructures, see Figure 3a.…”

Section: Plasmonic Resonances In Sersmentioning

confidence: 99%

Experimental tests of surface‐enhanced Raman scattering: Moving beyond the electromagnetic enhancement theory

Heeg

Mueller

Waßerroth

et al. 2020

J Raman Spectroscopy

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The electromagnetic enhancement theory describes surface‐enhanced Raman scattering (SERS) as a Raman effect that takes place in the near‐field of a plasmonic nanostructure. The theory has been very successful in explaining the fundamental properties of SERS, modelling the performance of different metals as enhancing materials and optimizing SERS hotspots for strongest possible enhancement. Over the last decade, a number of carefully designed experimental studies have examined predictions of the electromagnetic theory like the size and shape of SERS hotspots, the absolute magnitude of the enhancement and the width of the SERS resonance. Although the overall picture was quite satisfactory, the theory failed to predict key aspects of SERS, for example, the absolute magnitude of the plasmonic enhancement. We scrutinize these experiments and review them focusing on the results that require going beyond the electromagnetic enhancement theory. We argue that the results of these experiments create the need to develop the theory of SERS further, especially the exact role of plasmonic enhancement in inelastic light scattering.

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“…There are different theoretical approaches to expand the electromagnetic response of plasmonic nanostructures in terms of eigenmodes. These include a multipolar decomposition of the single nanoparticle plasmons [30][31][32][33] and the hybridization of different nanoparticle multipoles in oligomers [9,[34][35]. Here we use group theory [31,35] and the boundary elements method (BEM) [34].…”

Section: Methodsmentioning

confidence: 99%

Selective excitation of localized surface plasmons by structured light

Litvin¹,

Mueller²,

Reich³

2020

Opt. Express

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We investigated the selective excitation of localized surface plasmons by structured light. We derive selection rules using group theory and propose a fitting integral to quantify the contribution of the eigenmodes to the absorption spectra. Based on the result we investigate three nano oligomers of different symmetry (trimer, quadrumer, and hexamer) in detail using finitedifference time-domain simulations. We show that by controlling the incident light polarization and phase pattern we are able to control the absorption and scattering spectra. Additionally, we demonstrate that the fitting between the incident light and the oligomer modes may favor a number of modes to oscillate. Dark modes produce strong changes in the absorption spectrum and bright modes in the scattering spectrum. The experimental precision (axial shift error) may be on the same order as the oligomer diameter making the orbital angular momentum selection rules robust enough for experimental observation.

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Selection Rules for Structured Light in Nanooligomers and Other Nanosystems

Cited by 28 publications

References 87 publications

Nanowire Oligomer Waveguide Modes towards Reduced Lasing Threshold

Nanowire Oligomer Waveguide Modes towards Reduced Lasing Threshold

Experimental tests of surface‐enhanced Raman scattering: Moving beyond the electromagnetic enhancement theory

Selective excitation of localized surface plasmons by structured light

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