Surface lattice resonances and magneto-optical response in magnetic nanoparticle arrays

Abstract

Structuring metallic and magnetic materials on subwavelength scales allows for extreme confinement and a versatile design of electromagnetic field modes. This may be used, for example, to enhance magneto-optical responses, to control plasmonic systems using a magnetic field, or to tailor magneto-optical properties of individual nanostructures. Here we show that periodic rectangular arrays of magnetic nanoparticles display surface plasmon modes in which the two directions of the lattice are coupled by the magnetic field-controllable spin–orbit coupling in the nanoparticles. When breaking the symmetry of the lattice, we find that the optical response shows Fano-type surface lattice resonances whose frequency is determined by the periodicity orthogonal to the polarization of the incident field. In striking contrast, the magneto-optical Kerr response is controlled by the period in the parallel direction. The spectral separation of the response for longitudinal and orthogonal excitations provides versatile tuning of narrow and intense magneto-optical resonances.

Geometry dependence of surface lattice resonances in plasmonic nanoparticle arrays

“…The spin-orbit coupling terms proportional to σ x and σ y are not present here. However, we propose that they can be introduced by utilizing nontrivial particle shapes, or magnetic nanoparticles [22,23] where the two polarization (dipole orientation) directions are coupled due to intrinsic spin-orbit coupling in the magnetic material, and such couplings could be made momentum (k) dependent by designing the lattice geometry. It is especially interesting to envision that such nontrivial lattice systems may lead to new types of nanoscale lasing phenomena, so far observed only in simple square or rectangular lattices.…”

“…A white light-emitting diode (LED) is used as the light source, and a polarizer is placed before the spectrometer to control the polarization of the detected light. There is no magneto-optical response in silver nanoparticles in contrast to magnetic materials [22], and the nanoparticles are…”

“…SLRs have been utilized in light harvesting [10], emission control [11][12][13], strong light-matter interaction [14][15][16], and plasmonic lasing [17][18][19][20][21]. Recent works have also implemented SLRs in magnetoplasmonic responses in magnetic nanoparticle arrays [22,23], dark mode excitation in asymmetric dimer arrays [24], and superlattice plasmons in hierarchical gold particle arrays [25]. Even condensation phenomena have been theoretically studied [26].…”

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

“…Recently, the excitation of SLRs in arrays of ferromagnetic nickel nanoparticles was demonstrated [22]. The magneto-optical activity of an ordered ferromagnetic array is larger than that of randomly distributed nanoparticles, and it tunes sensitively with the period and symmetry of the lattice [22][23][24] or the size or shape of the nanoparticles [25]. The ability to compensate for intrinsic damping via the excitation of SLR modes offers new perspectives for refractive index sensing based on magnetoplasmonic architectures.…”

“…In the realm of noble-metal plasmonic sensors, various implementations of this approach have been studied [19][20][21]. Recently, the excitation of SLRs in arrays of ferromagnetic nickel nanoparticles was demonstrated [22]. The magneto-optical activity of an ordered ferromagnetic array is larger than that of randomly distributed nanoparticles, and it tunes sensitively with the period and symmetry of the lattice [22][23][24] or the size or shape of the nanoparticles [25].…”