Nanosystems with combined magnetic and plasmonic functionalities have in recent years become an active topic of research. By an adequate internal architecture of the constituting components, the magneto-optical activity of these systems can be greatly increased due to the electromagnetic field enhancement associated with the plasmon resonance. Simultaneously, the magnetic functionality permits the control of the plasmonic properties by an external magnetic field, which allows the development of active plasmonic devices. These materials find applications in, for example, gas and biosensing areas, and in integrated photonic devices for telecommunications. In the present work the state of the art and current understanding of the phenomenology associated with magnetoplasmonic structures where magnetism and plasmonics are intertwined are reviewed.

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Magnetoplasmonics: combining magnetic and plasmonic functionalities

This review provides a broad overview of the studies and effects of nonlocal response in metallic nanostructures. In particular, we thoroughly present the nonlocal hydrodynamic model and the recently introduced generalized nonlocal optical response (GNOR) model. The influence of nonlocal response on plasmonic excitations is studied in key metallic geometries, such as spheres and dimers, and we derive new consequences due to the GNOR model. Finally, we propose several trajectories for future work on nonlocal response, including experimental setups that may unveil further effects of nonlocal response.

https://iopscience.iop.org/article/10.1088/0953-8984/27/18/183204/pdf

Nonlocal optical response in metallic nanostructures

Plasmons and magnetoplasmons in semiconductor heterostructures

Tapered metal wires show a remarkable ability to ‘squeeze’ the lateral extent of a propagating surface-plasmon-polariton mode as it travels toward the tip of the taper. The transformation can be continued well below the diffraction limit to terminate at a nanoscale apex where intense near-fields are created. We perform the first full numerical simulations to investigate and quantify this phenomenon. We find optimal angles for maximal tip-field enhancement on conical wires by considering absorption, scattering to radiation and reflection. The optimal parameters we obtain contradict the conditions for adiabatic tapering, thereby advocating the use of numerical simulations. Despite the influence of losses, nanofocusing is still highly efficient for a broad range of practical metals, visible wavelengths and taper geometries. Diverse nano-optic applications can benefit directly and significantly from the results.

Optical Nanofocusing on Tapered Metallic Waveguides

We analyze subwavelength cylindrical holes in an optically thick metallic film with the metal described by a plasmonic model. We find that the dispersion diagram exhibits three distinct features that have a profound impact on the transmission of incident light through cylindrical holes. First, such holes always support propagating modes near the surface plasmon frequency, regardless of how small the holes are. Second, the fundamental plasmonic mode $({\mathrm{HE}}_{11})$ is located completely below the surface plasmon frequency and gives rise to a passband in the transmission spectrum. Third, when the radius of the holes is small, there exists a stop band, just above the surface plasmon frequency, where a normally incident plane wave does not transmit. Based on the dispersion analysis, we design both a single hole and a hole array in which propagating modes play a dominant role in the transport properties of incident light. These structures exhibit a different region of operation that has not been probed yet experimentally, while featuring a high packing density and diffractionless behavior.

/pdf/effect-of-the-plasmonic-dispersion-relation-on-the-4vvfv4k7y6.pdf

Effect of the plasmonic dispersion relation on the transmission properties of subwavelength cylindrical holes

The theory is given of the non-radiative surface plasmon-polariton modes of metal cylinders, modelled by a spatially dispersive free electron gas within a Bloch hydrodynamic formulation. Dispersion equations for homogeneous and inhomogeneous cylinders are derived for nth cylindrical harmonic, and the dispersion properties are investigated as a function of n, cylindrical radius and surface structure. The position, and splitting with n, of the surface modes is found to be considerably different from those based on a model that neglects spatial dispersion. This is particularly true for very small cylinder radii.

https://iopscience.iop.org/article/10.1088/0305-4608/10/1/014/pdf

B.V. Paranjape

Papers

Non-radiative surface plasma-polariton modes of inhomogeneous metal circular cylinders

High-density jellium-model calculation of force between half-planes of a nearly-free-electron metal at small separation

The surface plasmon modes of spherical voids in irradiated metals

Interaction between rare gas atoms outside metal surfaces: Role of plasma excitations

Surface plasmon in a parallel magnetic field