Electromagnetic Cavity Research Articles

Dyadic Green’s Function of Perfect Electromagnetic Conductor Rectangular Waveguides and Cavities

In this article, we present the dyadic Green’s functions (DGFs) for electric dipole excitation of perfect electromagnetic conductor (PEMC) rectangular waveguides and cavities. To derive the DGFs of a PEMC rectangular waveguide, we define two sets of orthogonal vector wave functions, that satisfy the boundary conditions at the waveguide walls. The theory of finding the DGF of this waveguide is based on the Ohm-Rayleigh method and orthogonal properties of the rectangular vector wave functions. By having the DGFs of this waveguide, one can derive the DGFs of a PEMC rectangular cavity using the scattering superposition (SSP) principle. The derived electric DGF of this waveguide is used to obtain the electric field propagated inside the waveguide due to an arbitrary current distribution. The distribution of the electric field inside the PEC, PMC, and PEMC waveguides will be obtained and compared with each other.

Electromagnetic rewarming for cryopreservation: A numerical comparison between multi-mode and single-mode electromagnetic cavity

Electromagnetic rewarming for cryopreservation: A numerical comparison between multi-mode and single-mode electromagnetic cavity

Resonant Polariton Thermal Transport Along a Vacuum Gap

Going with the flow: The authors show that, in contrast to the well-known cross-plane heat transport in a cavity, the in-plane transport increases with gap distance up to 1 cm, where it takes on a maximum value that increases with temperature. This resonance occurs due to the thermal activation of hundreds of electromagnetic cavity modes, which are standing waves in the cross-plane direction, yet propagate within the plane. The energy of these modes leads to thermal emission comparable to the radiation predicted by Planck's law, and this effect could be useful for generating and evacuating super-Planckian heat currents along macroscale cavities.

Nonclassical properties of a deformed atom-cavity field state

We analyse here a nonclassical state produced by an atom-cavity field interaction. The two-level atom is passed through the single-mode electromagnetic cavity field. By deforming the field operators and introducing nonlinearity to the classic Jaynes–Cummings model, we explore the system in respect of a nonlinear Hamiltonian. Assuming that the atom is in an excited state and the field is in a coherent state initially, the analytic expression for the state vector of the entire system state vector is obtained. With the help of the derived state vector, we calculate the photon number distribution, Mandel's parameter, Wigner function, anti-bunching, squeezing properties and Q function etc.

Comparison of 2.5D finite element formulations with perfectly matched layers for solving open axisymmetric electromagnetic cavity problems

AbstractAxial symmetry in time‐harmonic electromagnetic wave problems can be exploited by considering a Fourier expansion along the angular direction, reducing fully three‐dimensional computations to two‐dimensional ones on an azimuthal cross section. While this transition leads to a significant decrease in computational effort, it introduces additional difficulties, which necessitate appropriate finite element (FE) formulations. By combining the latter with perfectly matched layers (PML), open problems can be considered. In this work, we compare and discuss the performance of different combinations of axisymmetric FE formulations and PMLs, using a dielectric sphere in open space as a test case. As an application example, a superconducting Fabry–Pérot photon trap is considered.

A few results on permittivity variations in electromagnetic cavities

We study the eigenvalues of time-harmonic Maxwell's equations in a cavity upon changes in the electric permittivity ε of the medium. We prove that all the eigenvalues, both simple and multiple, are locally Lipschitz continuous with respect to ε. Next, we show that simple eigenvalues and the symmetric functions of multiple eigenvalues depend real analytically upon ε and we provide an explicit formula for their derivative in ε. As an application of these results, we show that for a generic permittivity all the Maxwell eigenvalues are simple.

Scalable single-mode surface-emitting laser via open-Dirac singularities.

Single-aperture cavities are a key component of lasers that are instrumental for the amplification and emission of a single light mode. However, the appearance of high-order transverse modes as the size of the cavities increases has frustrated efforts to scale-up cavities while preserving single-mode operation since the invention of the laser six decades ago1-8. A suitable physical mechanism that allows single-mode lasing irrespective of the cavity size-a 'scale invariant' cavity or laser-has not been identified yet. Here we propose and demonstrate experimentally that open-Dirac electromagnetic cavities with linear dispersion-which in our devices are realized by a truncated photonic crystal arranged in a hexagonal pattern-exhibit unconventional scaling of losses in reciprocal space, leading to single-mode lasing that is maintained as the cavity is scaled up in size. The physical origin of this phenomenon lies in the convergence of the complex part of the free spectral range in open-Dirac cavities towards a constant governed by the loss rates of distinct Bloch bands, whereas for common cavities it converges to zero as the size grows, leading to inevitable multimode emission. An unconventional flat-envelope fundamental mode locks all unit cells in the cavity in phase, leading to single-mode lasing. We name such sources Berkeley surface-emitting lasers (BerkSELs) and demonstrate that their far-field corresponds to a topological singularity of charge two, in agreement with our theory. Open-Dirac cavities unlock avenues for light-matter interaction and cavity quantum electrodynamics.

Core-shell heterogeneous graphene-based aerogel microspheres for high-performance broadband microwave absorption via resonance loss and sequential attenuation

Graphene-based aerogels have been attracted wide attention in microwave absorption (MA) for their lightweight and high-efficient absorption. However, the assembly design of their shape and structure is still lacking, bringing obstacles to the optimization of MA. Herein, we applied coaxial electrospinning to shape aerogel monoliths into aerogel microspheres (AMs) with core–shell bilayer structure, exhibiting distinguishing broadband and tunable high‐performance MA. The composite AMs including reduced oxide graphene/Fe3O4 shell layer and chitosan derived carbon core layer ([email protected]/Fe3O4) can be achieved via coaxial electrospinning-freeze frying followed by calcination. The core–shell structure can make electromagnetic wave sequential entry and attenuate, enhancing the impedance matching and electromagnetic wave propagation. Significantly, with a low loading of 5 wt%, the core–shell AMs exhibit a minimum reflection loss of − 61 dB at 13.84 GHz with the thickness of 2.5 mm, and the effective absorption bandwidth reach 6.88 GHz. More importantly, the corresponding absorption bandwidth is further widened to 7.52 GHz by adjusting the core–shell ratio. Electromagnetic simulation further indicate the core–shell bilayer coupling including electromagnetic wave sequential attenuation and cavity resonance loss can realize the enhanced broadband MA. The core–shell bilayer structure strategy paves a way to achieve graphene-based aerogel absorbers with high‐performance MA.

Guaranteed cost coherent control for quantum systems with non-quadratic perturbations in the system Hamiltonian

This paper considers a class of uncertain quantum systems subject to non-quadratic perturbations in the system Hamiltonian. Results on performance analysis for this class of systems are presented using a linear matrix inequality method. Guaranteed cost coherent controllers are designed through adding a controller Hamiltonian to the quantum systems. A numerical procedure is proposed for the controller synthesis to deal with a non-convex problem in the design process. An example of a quantum system comprised of a Josephson junction coupled to an electromagnetic resonant cavity is presented to illustrate the control method.

Nonlinear cooperative transfer of atomic energy in the vacuum field of the cavity

This paper researches the nonlinear cooperative transfer of atomic energy in the vacuum field of the cavity. Many scientists are concerned about a more detailed study of the cooperation interactions between different subsystems of quantum processes. Based on the theory of resonant interaction with two photons, between two active dipole atoms and a forbidden dipole in resonance with two photons, the author examines for the first time the resonance effect in two ways of the cavity. In some situations, the so-called quantum inseparability needs a new redefinition in order to describe the process that occurs between the photons belonging to these two modes of the cavity. In such a situation, it is better to study the quantum properties of collective modes arising from nonlinear interactions between traditional modes of the electromagnetic field cavity.

Schumann Resonance Modes and Ionosphere Parameters: An Annual Variability Comparison

<i>Schumann Resonance</i> (SR) signals result from an electromagnetic wave that propagates along the Earth-Ionosphere cavity. This signal is mainly characterized by the amplitude and frequency of the first modes; however, the relation with other variables that affect the Earth-ionosphere cavity is still undiscovered. In this paper, this relation is further explored with a methodology based on the usage of the first six SR modes and focusing on separating the data by the hour of the day. In this research, SR data is cross-correlated with 14 variables that affect the Electromagnetic cavity. The result shows preliminary evidence about the relationship between SR data and ionospheric related variables such as the Virtual Height of each Ionospheric layer or Solar Flux. The research outcome also provides substantial support for the importance of aggregating all the information contained in the first six modes and also reinforces the previous evidence about the significance of separating the SR variation by 24 hours to avoid the masking effect produced by the daily variability. This work also gives new perspectives for predictors based on SR modes.

Spectral stability of the curlcurl operator via uniform Gaffney inequalities on perturbed electromagnetic cavities

&lt;abstract&gt;&lt;p&gt;We prove spectral stability results for the $ curl curl $ operator subject to electric boundary conditions on a cavity upon boundary perturbations. The cavities are assumed to be sufficiently smooth but we impose weak restrictions on the strength of the perturbations. The methods are of variational type and are based on two main ingredients: the construction of suitable Piola-type transformations between domains and the proof of uniform Gaffney inequalities obtained by means of uniform a priori $ H^2 $-estimates for the Poisson problem of the Dirichlet Laplacian. The uniform a priori estimates are proved by using the results of V. Maz'ya and T. Shaposhnikova based on Sobolev multipliers. Connections to boundary homogenization problems are also indicated.&lt;/p&gt;&lt;/abstract&gt;

Wave functions for high-symmetry, thin microstrip antennas, and two-dimensional quantum boxes

For a spinless quantum particle in a one-dimensional box or an electromagnetic wave in a one-dimensional cavity, the respective Dirichlet and Neumann boundary conditions both lead to non-degenerate wave functions. However, in two spatial dimensions, the symmetry of the box or microstrip antenna is an important feature that has often been overlooked in the literature. In the high-symmetry cases of a disk, square, or equilateral triangle, the wave functions for each of those two boundary conditions are grouped into two distinct classes, which are one- and two-dimensional representations of the respective point groups, $C_{\infty v}$, $C_{4v}$, and $C_{3v}$. Here we present visualizations of representative wave functions for both boundary conditions and both one- and two-dimensional representations of those point groups. For the one-dimensional representations, color contour plots of the wave functions are presented. For the two-dimensional representations, the infinite degeneracies are presented as common nodal points and/or lines, the patterns of which are invariant under all operations of the respective point group. The wave functions with the Neumann boundary conditions have important consequences for the coherent terahertz emission from the intrinsic Josephson junctions in the high-temperature superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$: the enhancement of the output power from electromagnetic cavity resonances is only strong for wave functions that are not degenerate.

Magnomechanics in suspended magnetic beams

Cavity optomechanical systems have become a popular playground for studies of controllable nonlinear interactions between light and motion. Owing to the large speed of light, realizing cavity optomechanics in the microwave frequency range requires cavities up to several mm in size, hence making it hard to embed several of them on the same chip. An alternative scheme with much smaller footprint is provided by magnomechanics, where the electromagnetic cavity is replaced by a magnet undergoing ferromagnetic resonance, and the optomechanical coupling originates from magnetic shape anisotropy. Here, we consider the magnomechanical interaction occurring in a suspended magnetic beam -- a scheme in which both magnetic and mechanical modes physically overlap and can also be driven individually. We show that a sizable interaction can be produced if the beam has some initial static deformation, as is often the case due to unequal strains in the constituent materials. We also show how the magnetism affects the magnetomotive detection of the vibrations, and how the magnomechanics interaction can be used in microwave signal amplification. Finally, we discuss experimental progress towards realizing the scheme.

Rapid and Uniform REWARMING By Single-Mode Electromagnetic Resonance Cavity: Effect of Sample Shape

Rapid and Uniform REWARMING By Single-Mode Electromagnetic Resonance Cavity: Effect of Sample Shape

Coherently amplifying photon production from vacuum with a dense cloud of accelerating photodetectors

An accelerating photodetector is predicted to see photons in the electromagnetic vacuum. However, the extreme accelerations required have prevented the direct experimental verification of this quantum vacuum effect. In this work, we consider many accelerating photodetectors that are contained within an electromagnetic cavity. We show that the resulting photon production from the cavity vacuum can be collectively enhanced such as to be measurable. The combined cavity-photodetectors system maps onto a parametrically driven Dicke-type model; when the detector number exceeds a certain critical value, the vacuum photon production undergoes a phase transition from a normal phase to an enhanced superradiant-like, inverted lasing phase. Such a model may be realized as a mechanical membrane with a dense concentration of optically active defects undergoing gigahertz flexural motion within a superconducting microwave cavity. We provide estimates suggesting that recent related experimental devices are close to demonstrating this inverted, vacuum photon lasing phase.

Shape sensitivity analysis for electromagnetic cavities

We study the dependence of the eigenvalues of time‐harmonic Maxwell's equations in a cavity upon variation of its shape. The analysis concerns all eigenvalues both simple and multiple. We provide analyticity results for the dependence of the elementary symmetric functions of the eigenvalues splitting a multiple eigenvalue, as well as a Rellich‐Nagy‐type result describing the corresponding bifurcation phenomenon. We also address an isoperimetric problem and characterize the critical cavities for the symmetric functions of the eigenvalues subject to isovolumetric or isoperimetric domain perturbations and prove that balls are critical. We include known formulas for the eigenpairs in a ball and calculate the first one.

Computational analysis of hybrid heating of a heterogeneous core-shell configuration for improving temperature uniformity

Throughout this study, we propose using hybrid heating (microwaves – thermal radiation) on a heterogeneous structure. Our goal is to improve the effectivity of its thermal treatment. We analyze a core-shell assembly with different thermal and electrical properties. A solid sphere makes up the core of the arrangement. Such a core is surrounded by three layers of different materials. Because of the properties of the original system, we propose modifying the core so that it absorbs microwaves. The layers are all homogeneous and microwave transparent. The first two exhibit a low thermal conductivity, while the outermost one is a good thermal conductor. We also propose adding a thin layer of susceptor between the first two layers, striving to alleviate the low thermal conduction problem. Furthermore, the dielectric loss constant of this new layer is temperature-dependent. We assume that the composed sphere hangs within the electromagnetic cavity and continuously rotates, so it homogeneously receives microwaves and thermal radiation (from an electrical resistance). Thus, the thermal model is given by a set of time-dependent partial differential equations. Transient temperature profiles are analyzed under different experimental scenarios. There is a clear advantage of using the proposed hybrid heating in this particular case.

Charge-transfer chemical reactions in nanofluidic Fabry-Pérot cavities

We investigate the chemical reactivity of molecular populations confined inside a nanofluidic Fabry-P\'erot cavity. Due to strong light-matter interactions developing between a resonant electromagnetic cavity mode and the electric dipole moment of the confined molecules, a collective polariton excitation is formed. The former gets dressed by environmental vibrational and rotational degrees of freedom of the solvent. We call the resulting polariton dressed by its cloud of environmental excitation a ``reacton'', since it further undergoes chemical reactions. We characterize how the reacton formation modifies the kinetics of a photoisomerization chemical reaction involving an elementary charge-transfer process. We show that the reaction driving force and reorganization energy are both modulated optically by the reactant concentration, the vacuum Rabi splitting, and the detuning between the Fabry-P\'erot cavity frequency and targeted electronic transition. Finally, we compute the ultrafast picosecond dynamics of the whole photochemical reaction. We predict that despite optical cavity losses and solvent-mediated nonradiative relaxation, measurable signatures of the reacton formation can be found in state-of-the-art pump-probe experiments.

Strong Coupling of Antiferromagnetic Resonance with Subterahertz Cavity Fields

Strong coupling of electromagnetic cavity fields with antiferromagnetic spin waves in hematite ($\ensuremath{\alpha}$-${\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$) is achieved above room temperature. A cube of hematite is placed in a metallic tube and the transmission is measured, using a continuous-wave terahertz spectrometer. The spectra, collected as a function of the temperature, reveal the formation of magnetic polaritons.