Sensing with magnetic dipolar resonances in semiconductor nanospheres

Abstract

Abstract:In this work we propose two novel sensing principles of detection that exploit the magnetic dipolar Mie resonance in high-refractiveindex dielectric nanospheres. In particular, we theoretically investigate the spectral evolution of the extinction and scattering cross sections of these nanospheres as a function of the refractive index of the external medium (n ext ). Unlike resonances in plasmonic nanospheres, the spectral position of magnetic resonances in high-refractive-index nanospheres barely shifts as n ext changes. Nevertheless, there is a drastic reduction in the extinction cross section of the nanospheres when n ext increases, especially in the magnetic dipolar spectral region, which is accompanied with remarkable variations in the radiation patterns. Thanks to these changes, we propose two new sensing parameters, which are based on the detection of: i) the intensity variations in the transmitted or backscattered radiation by the dielectric nanospheres at the magnetic dipole resonant frequency, and ii) the changes in the radiation pattern at the frequency that satisfies Kerker's condition of near-zero forward radiation. To optimize the sensitivity, we consider several semiconductor materials and particles sizes. "Improved performance of aminopropylsilatrane over aminopropyltriehoxysilane as a linker for nanoparticlebased plasmon resonance sensors," Sens.

Size Dependence of the Directional Scattering Conditions on Semiconductor Nanoparticles

“…While the electric dipolar resonance (related to a 1 ) follows a behavior with the nanoparticle size close to the Fröhlich theory [15], the magnetic dipolar resonance is almost motionless [13]. As the directional phenomena are consequence of a coherent interference between these contributions, their size evolution should be related to those of the dipolar modes.…”

“…In fact, low-wavelength set in both cases is influenced by the quadrupolar modes and the emergence of the directional phenomena is not warranted. In Figures 1(c) and 1(d), it can be seen that those low wavelengths (vertical lines on the left) are close to sharp peaks in the extinction efficiency (see black dotted line) which correspond to quadrupolar resonances [10], [11], [13]. This effect is also the main responsible of the lack of results at certain size ranges in Figs.…”

“…The last important parameter, the particle size, has been also studied. A previous work [13] showed that while the electric resonances of semiconductor nanoparticles behave as plasmon ones, they are red shifted as the particle size increases; the magnetic ones are more stable and their spectral position remains unaltered as the size of the particle increases. This asymmetric behavior should be reflected into the spectral position of the directional conditions as the particle size changes, presenting a size evolution different from that of resonances.…”

“…While resonances are well-defined in spheres, they lose their sharp profile as the aspect ratio changes [12]. The dependence of both the spectral position of the resonances and their extinction efficiency on the surrounding medium have been already studied to use them as sensing parameters, following the works about plasmonic sensors [13]. The last important parameter, the particle size, has been also studied.…”

Thermally tunable polarization by nanoparticle plasmonic resonance in photonic crystal fibers

“…Other kinds of NPs such as Indium Tin Oxide NPs [37] or Ag NPs with dielectric encapsulation of SiO* [38,39] show resonances in the infrared region. Consequently, the concepts shown in this work could be applied to filters or polarizers working in the optical communication windows.…”