Interaction effects on the magneto-optical response of magnetoplasmonic dimers

Abstract

The effect that dipole-dipole interactions have on the magneto-optical (MO) properties of magnetoplasmonic dimers is theoretically studied. The specific plasmonic versus magnetoplasmonic nature of the dimer's metallic components and their specific location within the dimer play a crucial role in the determination of these properties. We find that it is possible to generate an induced MO activity in a purely plasmonic component, even larger than that of the MO one, therefore dominating the overall MO spectral dependence of the system. Adequate stacking of these components may allow one to obtain, for specific spectral regions, larger MO activities in systems with a reduced amount of MO metal and therefore with lower optical losses. Theoretical results are contrasted and confirmed with experiments for selected structures. Smart nanoscale systems are able to interact with light in an intricate fashion [1], which is strongly dependent on the internal electromagnetic interaction between the constituent elements of the system. Plasmonic structures composed of a number of individual elements, for example, give rise to Fano resonance effects that induce electromagnetically induced transparency (EIT) [2][3][4][5][6][7][8]. Similar phenomena have also been found in magnetoplasmonic nanosystems [9], i.e., those sharing magnetic and plasmonic functionalities and that therefore allow a further degree of freedom, namely, the external control of the system response [10][11][12][13][14]. By an adequate design of their internal structure, it is possible to obtain configurations which provide enhanced magnetooptical (MO) activity upon plasmon resonance excitation [15][16][17][18], which allow one to probe the electromagnetic (EM) field distribution inside a metallic nanoelement [19], or which yield high MO activity and low optical losses with MO figures of merit comparable with those of garnet structures [13]. Furthermore, in dimers where one of the elements is purely plasmonic and the other is of magnetoplasmonic nature, interaction effects cause the magnetoplasmonic component to induce MO activity in the plasmonic one (which intrinsically lacks MO activity) [20]. For specific interelement distances, which determine the interaction between them, this brings as a consequence the equivalent of the EIT in the MO spectrum of the system, i.e., a cancellation of the MO activity in a narrow spectral range due to the competition between the intrinsic MO contribution of the magnetoplasmonic component and the induced MO contribution of the plasmonic one [20]. As this effect exhibits a narrow spectral feature in the MO response, it may find applications in sensing and telecommunication areas, and a complete understanding will help in the development of novel sensing and biosensing architectures as well as MO devices.* a.garcia.martin@csic.esIn this context, these induced MO activity effects and their influence on the overall MO activity of the system for specific ranges of interaction lead to the consideration of additional issues where th...

Hybrid Ni/SiO2/Au dimer arrays for high-resolution refractive index sensing

“…The amplitude and phase relations of the four dipoles determine the optical and magneto-optical response of the Ni/SiO 2 /Au dimer in the far field [31,35,36]. In transmission geometry, the excitation of two orthogonal electric dipoles near the plasmon resonance condition causes the polarization of linearly polarized incident light to rotate and become elliptical.…”

“…In all these realizations, the magnetic constituent is in direct contact with the noble metal. Dimer nanodisks wherein a dielectric layer separates the ferromagnet and noble metal [31,35,36] and composite arrays of pure ferromagnetic and noble metal nanoparticles [24] have also been explored.…”

Magnetic Field Modification of Optical Magnetic Dipoles

“…This way, and in addition to the well-known case of plasmonic nanodisks exhibiting electric dipole resonances, in recent years it has also been demonstrated that nanoholes in optically thin metallic films exhibit "hole plasmon resonances" that resemble those of equivalent nanodisks. 24,25 This effect is so strong that has even allowed measuring the MO activity in pure noble metal resonant nanoelements. 16,17,18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 3 Apart from the obvious interest of investigating inverted systems exhibiting optical magnetism in the visible range, an open question is the feasibility of actually realizing an active control of this optical magnetism and the corresponding light-matter interaction.…”

Coupling phenomena and collective effects in resonant meta-atoms supporting both plasmonic and (opto-)magnetic functionalities: an overview on properties and applications [Invited]

“…Similarly to the results reported in refs. [129,130], also in this configuration the magnetic field-induced SLRs in the nickel nano-disks promote an enhancement of those in the gold ones, thus demonstrating that this approach may lead to new possibilities for the realization of tunable hybrid magneto-plasmonic crystals. A similar approach was also proposed previously by Caminale et al [146], who investigated the magnetooptical response of chemically synthesized iron oxide magnetic nanocrystals, optically coupled with ordered planar arrays of plasmonic meta-atoms, where they were able to arbitrary superimpose or detune the LSPRs of the nanoparticles arrays with respect to the dominant magneto-optical resonances of the magnetic meta-atoms to either merge or separate the purely plasmonic and the magnetic contributions in the magneto-optical spectrum to tune the enhancement of the magneto-optical signal.…”