Enhanced nonreciprocal effects in magnetoplasmonic systems supporting simultaneously localized and propagating plasmons.

Perforated magnetoplasmonic Au/Co/Au multilayers support both localized and propagating surface plasmon resonances. The presence of holes produces an enhancement of the magnetic field modulation of the propagating surface plasmon wavevector with respect to the isostructural continuous film in the spectral region corresponding to the hole associated localized plasmon resonance. This is due to the increased electromagnetic field in the surrounding area of the resonant hole, and the subsequent additional contribution to the magnetic modulation of the continuous film. This novel concept that gives rise to enhanced magnetic field induced nonreciprocal effects can be of interest in the development of innovative platforms for sensing applications, optical isolators and modulators.

Mimicking electromagnetically induced transparency in the magneto-optical activity of magnetoplasmonic nanoresonators.

We show that the interaction between a plasmonic and a magnetoplasmonic metallic nanodisk leads to the appearance of magneto-optical activity in the purely plasmonic disk induced by the magnetoplasmonic one. Moreover, at specific wavelengths the interaction cancels the net electromagnetic field at the magnetoplasmonic component, strongly reducing the magneto-optical activity of the whole system. The MO activity has a characteristic Fano spectral shape, and the resulting MO inhibition constitutes the magneto-optical counterpart of the electromagnetic induced transparency.

Magnetic modulation of surface plasmon modes in magnetoplasmonic metal-insulator-metal cavities.

The magnetic modulation of the surface plasmon-polariton (SPP) wavevector is experimentally and theoretically studied for the plasmonic modes excited in metal-insulator-metal (MIM) magnetoplasmonic cavities. For this purpose, Ag/SiO2/Ag multilayers with different SiO2 layer thickness in which a thin Co layer is positioned near the top Ag/SiO2 interface, near the bottom SiO2/Ag one, or near both of them, are studied. The magnetoplasmonic MIM cavities present symmetric (SM) and antisymmetric (AM) plasmonic modes, of different wavevector and electromagnetic field profiles inside the MIM cavity. We show that the magnetic SPP wavevector modulation strongly depends on which mode is considered, the cavity thickness, and the number and specific location of Co layers within the structure. With only one ferromagnetic layer, a net modulation is obtained, of higher magnitude as we reduce the SiO2 layer thickness. The introduction of a second Co layer in the structure reduces the modulation due to the non-reciprocal character of SPP modes under an applied magnetic field. Moreover, we demonstrate that the non-reciprocal nature of the SPP modulation can be experimentally visualized in the magnetic hysteresis loops under plasmon excitation conditions by using two Co layers with different magnetization switching fields.

Magneto-optical properties of core-shell magneto-plasmonic Au-Co(x)Fe(3 - x)O4 nanowires.

The magneto-optical properties of Au-Co(x)Fe(3 - x)O(4) core-shell nanowires embedded in porous alumina membranes are studied. The structures were obtained by depositing Co(x)Fe(3 - x)O(4) on the pore walls of alumina membranes by atomic layer deposition and filling the resulting nanotube with gold by electrodeposition. The effect of plasmon resonance excitation on the magneto-optical activity is clearly observed as a modification of the spectral line shape of the Kerr rotation signal.

Plasmon-induced magneto-optical activity in nanosized gold disks.

In this Letter we show that nanostructures made out of pure noble metals can exhibit measurable magneto-optic activity at low magnetic fields. This phenomenon occurs when the localized surface plasmon resonance of the nanostructure is excited in the presence of a static magnetic field parallel to the propagation of incident light. The large magneto-optical response observed comes from an increase of the magnetic Lorentz force induced by the large collective movement of the conduction electrons in the nanostructures when the resonance is excited.

Radiative corrections to the polarizability tensor of an electrically small anisotropic dielectric particle.

Radiative corrections to the polarizability tensor of isotropic particles are fundamental to understand the energy balance between absorption and scattering processes. Equivalent radiative corrections for anisotropic particles are not well known. Assuming that the polarization within the particle is uniform, we derived a closed-form expression for the polarizability tensor which includes radiative corrections. In the absence of absorption, this expression of the polarizability tensor is consistent with the optical theorem. An analogous result for infinitely long cylinders was also derived. Magneto optical Kerr effects in non-absorbing nanoparticles with magneto-optical activity arise as a consequence of radiative corrections to the electrostatic polarizability tensor.

Highly sensitive detection of biomolecules with the magneto-optic surface-plasmon-resonance sensor.

The characteristics of a novel magneto-optic surface-plasmon-resonance (MOSPR) sensor and its use for the detection of biomolecules are presented. This physical transduction principle is based on the combination of the magneto-optic activity of magnetic materials and a surface-plasmon resonance of metallic layers. Such a combination can produce a sharp enhancement of the magneto-optic effects that strongly depends on the optical properties of the surrounding medium, allowing its use for biosensing applications. Experimental characterizations of the MOSPR sensor have shown an increase in the limit of detection by a factor of 3 in changes of refractive index and in the adsorption of biomolecules compared with standard sensors. Optimization of the metallic layers and the experimental setup could result in an improvement of the limit of detection by as much as 1 order of magnitude.