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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

Polarization conversion calculations. For a system composed of nickel nanowires embedded in a dielectric medium with different refractive indexes, using (a) an SMM algorithm and (b) an EMA approximation. The schematics above show the parameters employed for each calculation. The nickel concentration in the system is the same in both calculations C = 18%.
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Figure 1: Polarization conversion calculations. For a system composed of nickel nanowires embedded in a dielectric medium with different refractive indexes, using (a) an SMM algorithm and (b) an EMA approximation. The schematics above show the parameters employed for each calculation. The nickel concentration in the system is the same in both calculations C = 18%.

Mentions: To investigate the influence of LSPs on the rps response, we considered an ordered hexagonal array of nickel nanowires embedded in a dielectric matrix and oriented along the z-axis. The diameter of the wires was set to 80 nm, with a lattice parameter of 180 nm and a height of 15 μm (a schematic view of the model system can be seen on top of Figure 1a). The spectral dependence of the absolute value of the polarization conversion /rps/ was obtained by means of a scattering matrix method (SMM), modified to allow MO activity in the polar configuration [15]. The diagonal and off-diagonal dielectric constants of nickel were taken from [16,17], respectively, whereas the refractive index of the dielectric matrix remained energy independent. Calculations were performed for different embedding mediums (from n = 1.7 to n = 1.4), shown in Figure 1a. A peak can be observed in all the spectra, blue-shifting and increasing its intensity, as the refractive index decreases. This peak is originated by an LSP excitation in the wires, as it was pointed out in [10,11], being its spectral position related to the variation of the plasmon resonance condition introduced by the modification of the dielectric background. We also performed additional calculations replacing the hexagonal array of nanowires with an effective layer. Since the dimensions of the nanostructure are much smaller than the wavelength of light, the optical properties of the nanowires and the embedding matrix can be merged by means of an effective medium approximation (EMA) [18]. The results are shown in Figure 1b. As it can be observed, the spectra show the LSP-induced peak, but contrary to the SMM results, its intensity decreases with the refractive index.


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)

Polarization conversion calculations. For a system composed of nickel nanowires embedded in a dielectric medium with different refractive indexes, using (a) an SMM algorithm and (b) an EMA approximation. The schematics above show the parameters employed for each calculation. The nickel concentration in the system is the same in both calculations C = 18%.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: Polarization conversion calculations. For a system composed of nickel nanowires embedded in a dielectric medium with different refractive indexes, using (a) an SMM algorithm and (b) an EMA approximation. The schematics above show the parameters employed for each calculation. The nickel concentration in the system is the same in both calculations C = 18%.
Mentions: To investigate the influence of LSPs on the rps response, we considered an ordered hexagonal array of nickel nanowires embedded in a dielectric matrix and oriented along the z-axis. The diameter of the wires was set to 80 nm, with a lattice parameter of 180 nm and a height of 15 μm (a schematic view of the model system can be seen on top of Figure 1a). The spectral dependence of the absolute value of the polarization conversion /rps/ was obtained by means of a scattering matrix method (SMM), modified to allow MO activity in the polar configuration [15]. The diagonal and off-diagonal dielectric constants of nickel were taken from [16,17], respectively, whereas the refractive index of the dielectric matrix remained energy independent. Calculations were performed for different embedding mediums (from n = 1.7 to n = 1.4), shown in Figure 1a. A peak can be observed in all the spectra, blue-shifting and increasing its intensity, as the refractive index decreases. This peak is originated by an LSP excitation in the wires, as it was pointed out in [10,11], being its spectral position related to the variation of the plasmon resonance condition introduced by the modification of the dielectric background. We also performed additional calculations replacing the hexagonal array of nanowires with an effective layer. Since the dimensions of the nanostructure are much smaller than the wavelength of light, the optical properties of the nanowires and the embedding matrix can be merged by means of an effective medium approximation (EMA) [18]. The results are shown in Figure 1b. As it can be observed, the spectra show the LSP-induced peak, but contrary to the SMM results, its intensity decreases with the refractive index.

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