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Unusual magneto-optical behavior induced by local dielectric variations under localized surface plasmon excitations.

González-Díaz JB, García-Martín A, Reig GA - Nanoscale Res Lett (2011)

Bottom Line: We study the effect of global and local dielectric variations on the polarization conversion rps response of ordered nickel nanowires embedded in an alumina matrix.When considering local changes, we observe a non-monotonous behavior of the rps, its intensity unusually modified far beyond to what it is expected for a monotonous change of the whole refractive index of the embedding medium.This is related to the local redistribution of the electromagnetic field when a localized surface plasmon is excited.

View Article: PubMed Central - HTML - PubMed

Affiliation: IMM-Instituto de Microelectrónica de Madrid (CNM-CSIC), Isaac Newton 8, PTM, Tres Cantos, E-28760 Madrid, Spain. juanb@imm.cnm.csic.es.

ABSTRACT
We study the effect of global and local dielectric variations on the polarization conversion rps response of ordered nickel nanowires embedded in an alumina matrix. When considering local changes, we observe a non-monotonous behavior of the rps, its intensity unusually modified far beyond to what it is expected for a monotonous change of the whole refractive index of the embedding medium. This is related to the local redistribution of the electromagnetic field when a localized surface plasmon is excited. This finding may be employed to develop and improve new biosensing magnetoplasmonic devices.

No MeSH data available.


Related in: MedlinePlus

(Graph) Theoretical spectra of the average EM field intensity within the Ni nanowires. For the same system described in Figure 1a. The continuous, dashed, short-dashed, and dotted lines correspond to a decreasing refractive index of the embedding medium (from n = 1.7 to n = 1.4, respectively). (Top) Unit cells employed in the FDTD calculations, showing the EM field distribution in the system at the energies where the LSP is excited (maximum field concentration within the nanowire). The dashed ring delimits the nanowire section.
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Figure 2: (Graph) Theoretical spectra of the average EM field intensity within the Ni nanowires. For the same system described in Figure 1a. The continuous, dashed, short-dashed, and dotted lines correspond to a decreasing refractive index of the embedding medium (from n = 1.7 to n = 1.4, respectively). (Top) Unit cells employed in the FDTD calculations, showing the EM field distribution in the system at the energies where the LSP is excited (maximum field concentration within the nanowire). The dashed ring delimits the nanowire section.

Mentions: The main reason why both calculations do not present similar evolutions of the polarization conversion is that the EMA approximation cannot take into account the strong increase of the EM field at the metallic nanoparticle. This can be better seen obtaining the EM field distribution within the nanowires at selected wavelengths. To do so, a 3D finite-difference time-domain (FDTD) simulation software was used (Lumerical Solutions, Inc., Vancouver, Canada), the results depicted in Figure 2 for the same parameters and refractive indexes used in the SMM calculations. The hexagons represent the unit cell showing the EM field intensity in the system at the energy where the LSP is excited. The field distribution is depicted on top of the nanostructure since its profile does not depend on the z-axis (just its intensity). The circle delimits the nanowire section. As it can be observed, the EM field tends to localize at the interface between the dielectric and the nanowire. When the refractive index of the matrix decreases, it appears less localized at the metal/dielectric interface, which is the expected for a plasmonic behavior. As a consequence, the EM field increases within the nanowires. Figure 2 shows this evolution with the refractive index, where we plot the average EM field spectra for different embedding matrices within the nanowires. The curves reproduce the same trend observed for the /rps/ calculations, i.e., the intensity increases as the refractive index decreases, thus pointing out that the strong relation between the polarization conversion and the amount of EM field within the nanowires induced by LSP excitations.


Unusual magneto-optical behavior induced by local dielectric variations under localized surface plasmon excitations.

González-Díaz JB, García-Martín A, Reig GA - Nanoscale Res Lett (2011)

(Graph) Theoretical spectra of the average EM field intensity within the Ni nanowires. For the same system described in Figure 1a. The continuous, dashed, short-dashed, and dotted lines correspond to a decreasing refractive index of the embedding medium (from n = 1.7 to n = 1.4, respectively). (Top) Unit cells employed in the FDTD calculations, showing the EM field distribution in the system at the energies where the LSP is excited (maximum field concentration within the nanowire). The dashed ring delimits the nanowire section.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211503&req=5

Figure 2: (Graph) Theoretical spectra of the average EM field intensity within the Ni nanowires. For the same system described in Figure 1a. The continuous, dashed, short-dashed, and dotted lines correspond to a decreasing refractive index of the embedding medium (from n = 1.7 to n = 1.4, respectively). (Top) Unit cells employed in the FDTD calculations, showing the EM field distribution in the system at the energies where the LSP is excited (maximum field concentration within the nanowire). The dashed ring delimits the nanowire section.
Mentions: The main reason why both calculations do not present similar evolutions of the polarization conversion is that the EMA approximation cannot take into account the strong increase of the EM field at the metallic nanoparticle. This can be better seen obtaining the EM field distribution within the nanowires at selected wavelengths. To do so, a 3D finite-difference time-domain (FDTD) simulation software was used (Lumerical Solutions, Inc., Vancouver, Canada), the results depicted in Figure 2 for the same parameters and refractive indexes used in the SMM calculations. The hexagons represent the unit cell showing the EM field intensity in the system at the energy where the LSP is excited. The field distribution is depicted on top of the nanostructure since its profile does not depend on the z-axis (just its intensity). The circle delimits the nanowire section. As it can be observed, the EM field tends to localize at the interface between the dielectric and the nanowire. When the refractive index of the matrix decreases, it appears less localized at the metal/dielectric interface, which is the expected for a plasmonic behavior. As a consequence, the EM field increases within the nanowires. Figure 2 shows this evolution with the refractive index, where we plot the average EM field spectra for different embedding matrices within the nanowires. The curves reproduce the same trend observed for the /rps/ calculations, i.e., the intensity increases as the refractive index decreases, thus pointing out that the strong relation between the polarization conversion and the amount of EM field within the nanowires induced by LSP excitations.

Bottom Line: We study the effect of global and local dielectric variations on the polarization conversion rps response of ordered nickel nanowires embedded in an alumina matrix.When considering local changes, we observe a non-monotonous behavior of the rps, its intensity unusually modified far beyond to what it is expected for a monotonous change of the whole refractive index of the embedding medium.This is related to the local redistribution of the electromagnetic field when a localized surface plasmon is excited.

View Article: PubMed Central - HTML - PubMed

Affiliation: IMM-Instituto de Microelectrónica de Madrid (CNM-CSIC), Isaac Newton 8, PTM, Tres Cantos, E-28760 Madrid, Spain. juanb@imm.cnm.csic.es.

ABSTRACT
We study the effect of global and local dielectric variations on the polarization conversion rps response of ordered nickel nanowires embedded in an alumina matrix. When considering local changes, we observe a non-monotonous behavior of the rps, its intensity unusually modified far beyond to what it is expected for a monotonous change of the whole refractive index of the embedding medium. This is related to the local redistribution of the electromagnetic field when a localized surface plasmon is excited. This finding may be employed to develop and improve new biosensing magnetoplasmonic devices.

No MeSH data available.


Related in: MedlinePlus