We study magnon-mediated optical transitions in micrometer-sized axially symmetric yttrium iron garnet (YIG) particles, which act as optomagnonic cavities, by means of electromagnetic calculations, treating the magneto-optical coupling to first order in perturbation theory, in the framework of a fully dynamic approach. Such particles with engineered shape anisotropy exhibit high-quality-factor Mie resonances in the infrared part of the spectrum, with a separation of few gigahertz, which matches the typical frequencies of magnons. This allows for optical transitions mediated by spin waves, while the micrometer volume favors stronger overlap between the optical modes and the precessing magnetization. Our results predict that photon-magnon coupling strengths of tens of kilohertz could be realized with cylindrical or spheroidal particles, since mainly the reduced volume, but also shape anisotropy, can lead to strong, up to four orders of magnitude, enhancement of the coupling strengths compared to submillimeter YIG spheres.

A variety of multidispersive, localized, or extended in frequency, bands, induced by inductance-based external electric circuits in piezoelectric phononic plates, is studied both theoretically and experimentally in this work. Their origin, tightly related to an equivalent LC-circuit behavior, is analyzed in detail and their interaction with the Lamb-like guided modes of the plate is also discussed. These bands, easily tuned by the choice of the parameters of the external electric circuitry, lead to a non-destructive, real-time control of the dispersion characteristics of these structures. Our device and analysis can find application in the improvement of surface acoustic wave components by offering additional degrees of freedom.

We employ the extended boundary condition method (EBCM) that we properly extend so as to describe gyroelectric and gyromagnetic (i.e., gyrotropic) anisotropy and report on the electromagnetic (EM) complex resonances of magnetooptic (i.e., gyroelectric) bodies of revolution (BoRs), as well as on the complex magnetic plasmon resonances (MPRs) of ferrite (i.e., gyromagnetic) BoRs. The proposed extension is based on an alternative scheme for the expansion of the EM field inside a gyrotropic medium, namely, a discrete eigenfunction (DE) expansion in terms of spherical vector wave functions (SVWFs). This approach provides the transition matrix (namely, T-matrix) that allows not only for the direct computation of the scattered field from the incident one, but also for the determination of the complex resonances of open (i.e., situated in free space) gyrotropic BoR resonators. The EBCM is validated on two levels: first, by calculating the EM scattering from various BoRs, including anisotropic spheroids, cylinders, and rods, and comparing with HFSS commercial software; second, by computing the complex eigenfrequency spectrum of gyroelectric spheroidal resonators and comparing with a recently developed rigorous technique for the EM modeling of anisotropic spheroids.

This chapter first summarizes the fundamentals of classical electrodynamics in continuous media, placing emphasis on the optical response of gyrotropic materials. It, subsequently, develops in a concise but rigorous manner the scattering- and transfer-matrix methods for general stratified photonic media, based on a versatile six-vector formulation of Maxwell equations. Applications are reported for periodic and defect one-dimensional (1D) magnetophotonic structures in different configurations. A consistent interpretation of some remarkable phenomena, such as occurrence of photonic gaps and localized defect modes, enhanced magnetooptical effects, non-reciprocal optical response, etc., is provided through a thorough analysis of relevant dispersion diagrams in conjunction with transmission/reflection spectra. Finally, the concept of a dual optomagnonic cavity, formed in judiciously designed stratified magnetophotonic structures, for strong photon–magnon interaction is introduced. Methods for its theoretical description, namely the Green’s function-based perturbation expansion, the quasi-static adiabatic approximation, and a fully dynamic time-Floquet approach, are developed, and their accuracy and limits of validity are assessed. Proof-of-concept demonstrations are presented for enhanced interaction of light, trapped in optical defect modes, with perpendicular standing spin waves, in a dielectric magnetic film sandwiched between two dielectric Bragg mirrors.

A rigorous time Floquet method for the calculation of scattering of electromagnetic waves by a homogeneous spherical object, characterized by a periodically varying-in-time isotropic permittivity, is presented. The method is applied to the study of Mie scattering by such a modulated dielectric particle. Our results are in excellent agreement with the quasistatic adiabatic approximation in the slow-modulation limit. At higher modulation frequencies, a remarkable spectral response, including resonant inelastic scattering and frequency conversion as well as energy transfer between the dynamic sphere and the electromagnetic field, is revealed and consistently explained.