Plasmon spectra of nanospheres under a tightly focused beam

Mojarad, Nassiredin M.; Sandoghdar, Vahid; Agio, Mario

doi:10.1364/josab.25.000651

Cited by 63 publications

(77 citation statements)

References 46 publications

(90 reference statements)

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“…Such field distributions can be generated, for instance, by tight focussing of polarized light beams [7][8][9][10] . To guarantee high quality and resolution in the investigation of objects with sub-wavelength dimensions, the precise knowledge of the spatial distribution of the exciting vectorial field is of utmost importance.…”

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confidence: 99%

Nanointerferometric amplitude and phase reconstruction of tightly focused vector beams

et al. 2013

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Highly confined vectorial electromagnetic field distributions represent an excellent tool for detailed studies in nano-optics and high resolution microscopy, such as nonlinear microscopy 1 , advanced fluorescence imaging 2-4 or nanoplasmonics 5,6 . Such field distributions can be generated, for instance, by tight focussing of polarized light beams [7][8][9][10] . To guarantee high quality and resolution in the investigation of objects with sub-wavelength dimensions, the precise knowledge of the spatial distribution of the exciting vectorial field is of utmost importance. Full-field reconstruction methods presented so far involved, for instance, complex near-field techniques 11,12 . Here, we demonstrate a simple and straight-forward to implement measurement scheme and reconstruction algorithm based on the scattering signal of a single spherical nanoparticle as a field-probe. We are able to reconstruct the amplitudes of the individual focal field components as well as their relative phase distributions with sub-wavelength resolution from a single scan measurement without the need for polarization analysis of the scattered light. This scheme can help to improve modern microscopy and nanoscopy techniques.In the optical analysis of sub-wavelength objects such as cellular structures 13 , plasmonic particles 5,6,14 or single spins 3 , nano-optical tools including highly resolving microscopy techniques are used. Because such methods utilise complex and highly confined vector fields, the exact knowledge of the corresponding spatial field distributions is crucial. In the last decades, several techniques have been proposed to map these focal fields, such as using metal knife edges 15,16 to probe the total electric energy density distribution, fluorescence molecules 17 , tapered fibres 18,19 or tip-based methods 12 to image specific field orientations, or near-field scanning optical microscope (NSOM) techniques to extract amplitude and even phase information 11 . These NSOM-based methods require complex measurement and detection schemes and calibration procedures to allow for amplitude and phase a) Electronic mail: thomas.bauer@mpl.mpg.de mapping of individual field components. As an alternative approach for measuring phase information also a single particle scattering scheme was proposed recently 22 , where the authors show that Mie-scattering can distinguish the topological charge of vortex-beams.We now demonstrate a precise and easily implementable field reconstruction technique for highly confined field distributions created by arbitrary focusing systems, based on, what we call, Mie-scattering nanointerferometry. The basic concept of this reconstruction method for highly confined focal field distributions can be understood as follows. We use a metallic nanosphere on a glass substrate as local field sensor and scan it stepwise through the focal field distribution under investigation. If the particle size is chosen small enough, it will be excited by the local electric field E(r 0 ) only. Its response can be described,...

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Nanointerferometric amplitude and phase reconstruction of tightly focused vector beams

et al. 2013

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“…Although the definitions of extinction, scattering and absorption cross sections typically employed for plane wave excitation cannot be applied to focused beams, one can calculate the power scattered and absorbed by the particles and 4 their sum (henceforth considered as extinguished power) by proper integration of the Poynting vectors. 38 Explicit expressions for the expansion coefficients for the incident field as well as for the scattered, absorbed and extinguished power are given in the Methods section.…”

Section: Resultsmentioning

confidence: 99%

“…Since the numerical aperture of the system is moderate, these results are quantitatively similar to the case of plane wave excitation. 38 39 Next, we assume that the lens is illuminated by an AP beam. In this case the spectra are dominated by a resonance at 2.76 eV.…”

Section: Resultsmentioning

confidence: 99%

Dark Modes and Fano Resonances in Plasmonic Clusters Excited by Cylindrical Vector Beams

2012

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Control of the polarization distribution of light allows tailoring the electromagnetic response of plasmonic particles. By rigorously extending the generalized multiparticle Mie theory, we show that focused cylindrical vector beams (CVB) can be used to efficiently excite dark plasmon modes in nanoparticle clusters. In addition to the small radiative damping and large field enhancement associated to dark modes, excitation with CVB can give place to unusual phenomenology like the formation of electromagnetic cold spots and the generation of Fano resonances in highly symmetric clusters. Overall, the results show the potential of CVB to tailor the plasmonic response of nanoparticle clusters in a unique way.

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“…In the present work we consider also other illuminations schemes that can be implemented in the same calculation scheme by expanding the incident field in vector spherical harmonics. Thus, a focused plane wave can be treated with the multipolar expansion developed by Sheppard and Török, 40 that has been used to study the influence of tight focusing on the plasmon spectra of single particles 41 and particle dimers 39 . As the degree of focusing increases, the relative weight of high order vector spherical harmonics decreases 40,41 .…”

Section: Methodsmentioning

confidence: 99%

“…However, control on the excitation of different multipolar orders can be addressed by adjusting the illumination conditions. It has been shown that higher order resonances can be quenched by using strongly focused beams, both in single particles 41 and particle clusters 39 . We can consider the effect of focused plane waves by the extension of the generalized Mie theory described in Section 2.…”

Section: Illumination Conditionsmentioning

confidence: 99%

Boosting Fano resonances in single layered concentric core–shell particles

Sancho‐Parramon

Jelovina

2014

Nanoscale

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Efficient excitation of Fano resonances in plasmonic systems usually requires complex nano-structure geometries and some degree of symmetry breaking. However, a single-layer concentric core-shell particle presents inherent Fano profiles in the scattering spectra when sphere and cavity modes spectrally overlap. Weak hybridization and proper choice of core and shell materials gives place to strong electric dipolar Fano resonances in these systems and retardation effects can result in resonances of higher multipolar order or of magnetic type. Furthermore, proper tailoring of illumination conditions leads to an enhancement of the Fano resonance by quenching of unwanted electromagnetic modes. Overall, it is shown that single layer core-shell particles can act as robust Fano resonators.

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Plasmon spectra of nanospheres under a tightly focused beam

Cited by 63 publications

References 46 publications

Nanointerferometric amplitude and phase reconstruction of tightly focused vector beams

Nanointerferometric amplitude and phase reconstruction of tightly focused vector beams

Dark Modes and Fano Resonances in Plasmonic Clusters Excited by Cylindrical Vector Beams

Boosting Fano resonances in single layered concentric core–shell particles

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