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

Active plasmonics is a burgeoning and challenging subfield of plasmonics. It exploits the active control of surface plasmon resonance. In this review, a first-ever in-depth description of the theoretical relationship between surface plasmon resonance and its affecting factors, which forms the basis for active plasmon control, will be presented. Three categories of active plasmonic structures, consisting of plasmonic structures in tunable dielectric surroundings, plasmonic structures with tunable gap distances, and self-tunable plasmonic structures, will be proposed in terms of the modulation mechanism. The recent advances and current challenges for these three categories of active plasmonic structures will be discussed in detail. The flourishing development of active plasmonic structures opens access to new application fields. A significant part of this review will be devoted to the applications of active plasmonic structures in plasmonic sensing, tunable surface-enhanced Raman scattering, active plasmoni...

Active Plasmonics: Principles, Structures, and Applications

A detailed discussion of the properties of bulk polaritons in an isotropic dielectric, with a single infrared active optical phonon is given. The phonon and photon strength functions, which provide a useful means of characterizing the polariton are introduced, and polaritons examined in magnetic crystals, anisotropic dielectrics, materials in which spatial dispersion effects and absorption are important. Experimental methods of studying polaritons are reviewed, with emphasis on Raman scattering, non-linear interactions between polaritons and recent experimental studies of non-linear optical phenomena where polaritons in the intermediate state play an important role. The properties of surface polaritons at the interfaces of the isotropic dielectric, anisotropic dielectrics and magnetic media, and experimental methods for the study of surface polaritons are also discussed. The paper concludes with the comparison between the properties of coupled magnon-phonon modes in magnetic crystals and polaritons.

https://iopscience.iop.org/article/10.1088/0034-4885/37/7/001/pdf

Polaritons: the electromagnetic modes of media

Plasmons and magnetoplasmons in semiconductor heterostructures

A century-old tenet in physics and engineering asserts that any type of system, having bandwidth Δω, can interact with a wave over only a constrained time period Δt inversely proportional to the bandwidth (Δt·Δω ~ 2π). This law severely limits the generic capabilities of all types of resonant and wave-guiding systems in photonics, cavity quantum electrodynamics and optomechanics, acoustics, continuum mechanics, and atomic and optical physics but is thought to be completely fundamental, arising from basic Fourier reciprocity. We propose that this "fundamental" limit can be overcome in systems where Lorentz reciprocity is broken. As a system becomes more asymmetric in its transport properties, the degree to which the limit can be surpassed becomes greater. By way of example, we theoretically demonstrate how, in an astutely designed magnetized semiconductor heterostructure, the above limit can be exceeded by orders of magnitude by using realistic material parameters. Our findings revise prevailing paradigms for linear, time-invariant resonant systems, challenging the doctrine that high-quality resonances must invariably be narrowband and providing the possibility of developing devices with unprecedentedly high time-bandwidth performance.

Breaking Lorentz reciprocity to overcome the time-bandwidth limit in physics and engineering

A theory of surface magnetoplasmons in semiconductors is developed with the inclusion of retardation for the geometry in which the magnetic field is parallel to the surface and the direction of propagation is perpendicular to the magnetic field. If the background dielectric constant ${\ensuremath{\epsilon}}_{\ensuremath{\infty}}$ lies in a suitable range for a given value of the magnetic field, gaps appear in the dispersion relation for the surface magnetoplasmons. The possible experimental observation of these gaps is discussed.

J. J. Brion

Papers

Theory of Surface Magnetoplasmons in Semiconductors