Unveiling ultrasharp scattering–switching signatures of layered gold–dielectric–gold nanospheres

Sikdar, Debabrata; Rukhlenko, Ivan D.; Cheng, Wenlong; Premaratne, Malin

doi:10.1364/josab.30.002066

Cited by 21 publications

(8 citation statements)

References 45 publications

(62 reference statements)

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“…† For the NPs with diameter of around 12.8 nm, we have additionally incorporated the sizedependent corrections to the permittivity model to account for enhanced scattering losses of surface electrons at NP boundaries. 42,43 In what follows, the 2D layer of NPs can be further characterized by an anisotropic dielectric tensor, whose parallel ε k 1 (ω) and perpendicular ε ? 1 (ω) components satisfy the following relations: 39,40…”

Section: Resultsmentioning

confidence: 99%

Tuneable 2D self-assembly of plasmonic nanoparticles at liquid|liquid interfaces

et al. 2016

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Understanding the structure and assembly of nanoparticles at liquid|liquid interfaces is paramount to their integration into devices for sensing, catalysis, electronics and optics. However, many difficulties arise when attempting to resolve the structure of such interfacial assemblies. In this article we use a combination of X-ray diffraction and optical reflectance to determine the structural arrangement and plasmon coupling between 12.8 nm diameter gold nanoparticles assembled at a water|1,2-dichloroethane interface. The liquid|liquid interface provides a molecularly flat and defect-correcting platform for nanoparticles to self-assemble. The amount of nanoparticles assembling at the interface can be controlled via the concentration of electrolyte within either the aqueous or organic phase. At higher electrolyte concentration more nanoparticles can settle at the liquid|liquid interface resulting in a decrease in nanoparticle spacing as observed from X-ray diffraction experiments. The plasmonic coupling between the nanoparticles as they come closer together is observed by a red-shift in the optical reflectance spectra. The optical reflectance and the X-ray diffraction data are combined to introduce a new 'plasmon ruler'. This allows extraction of structural information from simple optical spectroscopy techniques, with important implications for understanding the structure of self-assembled nanoparticle films at liquid interfaces.

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Section: Resultsmentioning

confidence: 99%

Tuneable 2D self-assembly of plasmonic nanoparticles at liquid|liquid interfaces

et al. 2016

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“…Metallic nanoparticle antennas-by virtue of surface plasmon resonances in their optical responsehave already evidenced numerous exciting possibilities like directed narrow-band scattering, resonance-enhanced wideband absorption, and intense near-field confinement as well as enhancement [2,3]. These properties made the plasmonic nanoantennas feature in a wide spectrum of applications ranging from light harvesting to biological/chemical sensing, and from waveguiding to photothermal therapeutics [4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Cubic, or in general rectangular cuboid, nanoparticles are usually preferable for such applications owing to their broad resonance tunability, comparatively large optical coefficients, and relative ease of fabrication [18].…”

Section: Introductionmentioning

confidence: 99%

Substrate-Mediated Broadband Tunability in Plasmonic Resonances of Metal Nanoantennas on Finite High-Permittivity Dielectric Substrate

et al. 2015

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We investigate the optical response of a gold nanocube antenna supported by a high-permittivity dielectric nanocuboid substrate and propose schemes for broadband tailoring of its plasmonic resonances via alteration in image-charge screening. Based on finite-elementmethod (FEM) simulations-in agreement with filteredcoupled-dipole-approximations (FCDA)-we explore the tunability and spectral evolution of the substrate-supported nanocube's hybridized plasmon modes as functions of the relative permittivity and dimensions of the dielectric substrate. Besides numerical calculations, we also derive simple analytical expressions using image-charge theory to readily estimate the resonance spectral shift-gauging the intense particle-substrate interaction-for a substratesupported nanocube. Strong localized electric field, around the nanocube's vertices and edges near the substrate, is observed due to the image charges induced in the substrate by the coupled bonding mode arising from hybridization of the primitive dipolar and quadrupolar modes of the nanocube. By introducing slots on the dielectric substrate in the areas around the nanocube's edges where electric field is highly concentrated, we achieve substrate's surfacemediated wideband tunability of plasmonic resonance as functions of the geometric parameters of the slots while maintaining the overall dimensions and material of the nanocuboid substrate. These slots enable dynamic tunability of plasmon resonance by placing graphene flakes on them, which facilitates electrical tailoring of nanocube's plasmon resonance over visible and near-infrared regions. Thus, these proposed schemes would allow one to widely tune the optical responses of any plasmonic nanoantennas using a slotted finite high-permittivity-dielectric substrate for numerous applications in nanophotonic integrated circuits and plasmonic devices.

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“…Consider the same multilayer sphere schematically shown in the inset of Figure a, but with the metal layers being silver (complex permittivity from experimental data) instead. Similar metal-dielectric-metal nanospheres have been synthesized , and studied numerically ,− in prior works. To mimic potential experimental condition, we consider such nanospheres suspended in an aqueous solution (ε = 1.77).…”

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Theoretical Criteria for Scattering Dark States in Nanostructured Particles

et al. 2014

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Nanostructures with multiple resonances can exhibit a suppressed or even completely eliminated scattering of light, called a scattering dark state. We describe this phenomenon with a general treatment of light scattering from a multi-resonant nanostructure that is spherical or non-spherical but subwavelength in size. With multiple resonances in the same channel (i.e. same angular momentum and polarization), coherent interference always leads to scattering dark states in the low-absorption limit, regardless of the system details. The coupling between resonances is inevitable and can be interpreted as arising from far-field or near-field. This is a realization of coupled- and interference effects. 5-9 A particularly interesting phenomenon is the suppressed scattering in nanostructures with multiple plasmonic resonances, [10][11][12][13][14][15][16][17][18][19][20][21][22][23] plasmonic and excitonic resonances, [24][25][26][27][28][29][30] or dielectric resonances, 31,32 referred to collectively as a "scattering dark state." A wealth of models has been employed to describe this suppressed scattering, ranging from perturbative models, 12 generalization of the Fano formula, 13-15 and electrostatic approximation, 22,23 to coupled-mechanical-oscillator models. 17-21 These models reveal valuable insights and facilitate the design of specific structures with desired line shapes. However, the general criteria for observing such scattering dark states remain unclear. Non-scattering states have been known in atomic physics since the early works of Fano 33 and have been discovered in a variety of nanoscale systems in recent years [5][6][7][8]34,35 . However, Fano resonances generally concern the interference between a narrow discrete resonance and a broad resonance or continuum. Meanwhile, many occurrences of the scattering dark state involve the interference between multiple narrow discrete resonances, and it seems necessary to treat the multiple resonances at equal footing. Thus, we seek a formalism analogous to the phenomenon of coupled-resonator-induced transparency 5 that has been established in certain other systems such as coupled mechanical oscillators 36,37 , coupled cavities 38,39 , coupled microring resonators [40][41][42][43][44] , and planar metamaterials [45][46][47][48] .Here, we derive the general equations governing the resonant light scattering from a spherical or a non-spherical but subwavelength obstacle, accounting for multiple resonances with low loss. Due to the spherical symmetry (or the small size) of the obstacle, different channels of the multipole fields are decoupled. We find that within each channel, n resonances always lead to n − 1 scattering dark states in the low-absorption limit. This universal result is independent of the radiative decay rates of the resonances, method of coupling (can be 3 near-field or far-field), nature of the resonances (can be plasmon, exciton, whispering-gallery, etc.), number of resonances, which of the multipole, TE or TM polarization, and other system det...

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Unveiling ultrasharp scattering–switching signatures of layered gold–dielectric–gold nanospheres

Cited by 21 publications

References 45 publications

Tuneable 2D self-assembly of plasmonic nanoparticles at liquid|liquid interfaces

Tuneable 2D self-assembly of plasmonic nanoparticles at liquid|liquid interfaces

Substrate-Mediated Broadband Tunability in Plasmonic Resonances of Metal Nanoantennas on Finite High-Permittivity Dielectric Substrate

Theoretical Criteria for Scattering Dark States in Nanostructured Particles

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