Mode Of Electromagnetic Field Research Articles

Large area photonic crystal cavities: a local density approach.

Large area photonic crystal cavities are devices of interest for photovoltaics, optoelectronics, and solid-state lighting. However, depending on their dimensions they pose a large computational challenge. Here, we use a local density approach to avoid direct simulation of the device. We capture the effect of both ideal and distorted photonic crystals in an effective mass and an effective potential. We use these to map the problem of calculating the electromagnetic field modes to solving a simple time-independent Schrödinger equation. We show that, in the case that the hole radius varies quadratically as a function of position, the eigenmodes of the photonic crystals can be described by the corresponding eigenmodes of the quantum harmonic oscillator with typical agreements well above 90%.

General integrable n-level, many-mode Janes-Cummings-Dicke models and classical r-matrices with spectral parameters

Using the technique of classical r-matrices and quantum Lax operators, we construct the most general form of the quantum integrable “n-level, many-mode” spin-boson Jaynes-Cummings-Dicke-type hamiltonians describing an interaction of a molecule of N n-level atoms with many modes of electromagnetic field and containing, in general, additional non-linear interaction terms. We explicitly obtain the corresponding quantum Lax operators and spin-boson analogs of the generalized Gaudin hamiltonians and prove their quantum commutativity. We investigate symmetries of the obtained models that are associated with the geometric symmetries of the classical r-matrices and construct the corresponding algebra of quantum integrals. We consider in detail three classes of non-skew-symmetric classical r-matrices with spectral parameters and explicitly obtain the corresponding quantum Lax operators and Jaynes-Cummings-Dicke-type hamiltonians depending on the considered r-matrix.

Photo-generated THz plasmonic waveguides

We propose a novel method to actively control the propagation of THz surface plasmon polaritons in plasmonic waveguides. This method relies on the excitation of long range surface plasmon polaritons (LRSPPs) in thin slabs of semiconductors. The characteristics of LRSPPs (electromagnetic field confinement and mode propagation length) can be precisely tuned by optically pumping charge carriers to the conduction band of the semiconductor. This excitation can be local by illuminating a flat semiconductor slab with an expanded optical beam that is structured with the shape of the THz waveguide. In this way, it may be possible to design active and integrated THz circuits by simply changing the illumination pattern on the surface.

Heat-machine control by quantum-state preparation: from quantum engines to refrigerators.

We explore the dependence of the performance bounds of heat engines and refrigerators on the initial quantum state and the subsequent evolution of their piston, modeled by a quantized harmonic oscillator. Our goal is to provide a fully quantized treatment of self-contained (autonomous) heat machines, as opposed to their prevailing semiclassical description that consists of a quantum system alternately coupled to a hot or a cold heat bath and parametrically driven by a classical time-dependent piston or field. Here, by contrast, there is no external time-dependent driving. Instead, the evolution is caused by the stationary simultaneous interaction of two heat baths (having distinct spectra and temperatures) with a single two-level system that is in turn coupled to the quantum piston. The fully quantized treatment we put forward allows us to investigate work extraction and refrigeration by the tools of quantum-optical amplifier and dissipation theory, particularly, by the analysis of amplified or dissipated phase-plane quasiprobability distributions. Our main insight is that quantum states may be thermodynamic resources and can provide a powerful handle, or control, on the efficiency of the heat machine. In particular, a piston initialized in a coherent state can cause the engine to produce work at an efficiency above the Carnot bound in the linear amplification regime. In the refrigeration regime, the coefficient of performance can transgress the Carnot bound if the piston is initialized in a Fock state. The piston may be realized by a vibrational mode, as in nanomechanical setups, or an electromagnetic field mode, as in cavity-based scenarios.

Metallic strip gratings in the sub-subwavelength regime.

Metallic strip gratings (MSG) have different applications, ranging from printed circuits to filters in microwave domains. When they are under the influence of an electromagnetic field, evanescent and/or abnormal modes appear in the region between the traces, their utilization leading to the development of new electromagnetic nondestructive evaluation methods. This paper studies the behavior of MSGs in the sub-subwavelength regime when they are excited with TEz or TMz polarized plane waves and the slits are filled with different dielectrics. The appearance of propagating, evanescent and abnormal modes is emphasized using an electromagnetic sensor with metamaterials lens realized with two conical Swiss rolls, which allows the extraction of the information carried by the guided evanescent waves. The evanescent waves, manipulated by the electromagnetic sensor with metamaterial lenses, improve the electromagnetic images so that a better spatial resolution is obtained, exceeding the limit imposed by diffraction. Their theoretical and experimental confirmation opens the perspective for development of new types of sensors working in radio and microwave frequencies.

Synchronization in a mechanical resonator array coupled quadratically to a common electromagnetic field mode.

Optomechanical systems are based on the nonlinear coupling between the electromagnetic (EM) field in a resonator and one or more bulk mechanical resonators such that the frequency of the EM field resonator depends on the displacement coordinates of each of the mechanical resonators. In this paper we consider the case of multiple mechanical resonators interacting with a common field for which the frequency of the EM resonance is tuned to depend quadratically (to lowest order) on the displacement of the resonators. By using the method of amplitude equations around a critical point, it is shown that groups of near-identical bulk mechanical resonators with low driving fail to synchronize unless their natural frequencies are identical, in which case the resulting system can exhibit multistability.

一种用于微小型铷原子频标的6.83 GHz谐振腔

研制了一种用于微小型铷原子频标的6.83 GHz微波谐振腔。对谐振腔内的电磁场、谐振频率与探针的关系进行了分析，并应用Ansoft HFSS软件进行填充介质的谐振腔进行了仿真分析。在此基础上对介质谐振腔进行设计与加工制造，测量出填充不同厚度的氧化铝陶瓷时谐振腔的谐振频率。结果表明，当矩形谐振腔取12 mm × 15 mm × 18 mm，填充5.66 mm厚的氧化铝陶瓷介质，介质谐振腔频率可达6.83 GHz，模式为TE101，谐振腔体积大幅减小至3.24 cm3, 是传统的未填充谐振腔体积的三分之一，同时电磁场分布均匀，适用于铷气室型微小型原子频标。 This paper presents a 6.83 GHz microwave cavity for miniaturized rubidium atomic frequency standard. Electromagnetic fields in the microwave cavity are analyzed, and relationships of the resonance frequency and the size of the field excitation probe are studied. The Ansoft HFSS software is used to simulate the electromagnetic distributions in microwave cavity. Based on these analyses, the microwave cavity is manufactured. By using the vector network analyzer, the S11 parameters for the micro- wave cavity filled with different thickness of aluminum oxide ceramics are acquired. Tested results demonstrate that the electromagnetic field mode is TE101 when the resonance frequency reaches 6.83 GHz, and cavity size is 12 mm × 15 mm × 18 mm with the thickness of filled aluminum oxide ceramics (96%) of 5.66 mm. The volume of the developed 6.83 GHz microwave cavity is 3.24 cm3, which is about 1/3 of the volume of the conventional unfilled cavity. It fits very well for loading the MEMS- based rubidium filter cell and absorption cell for miniaturized rubidium atomic frequency standards. This paper presents a 6.83 GHz microwave cavity for miniaturized rubidium atomic frequency standard. Electromagnetic fields in the microwave cavity are analyzed, and relationships of the resonance frequency and the size of the field excitation probe are studied. The Ansoft HFSS software is used to simulate the electromagnetic distributions in microwave cavity. Based on these analyses, the microwave cavity is manufactured. By using the vector network analyzer, the S11 parameters for the micro- wave cavity filled with different thickness of aluminum oxide ceramics are acquired. Tested results demonstrate that the electromagnetic field mode is TE101 when the resonance frequency reaches 6.83 GHz, and cavity size is 12 mm × 15 mm × 18 mm with the thickness of filled aluminum oxide ceramics (96%) of 5.66 mm. The volume of the developed 6.83 GHz microwave cavity is 3.24 cm3, which is about 1/3 of the volume of the conventional unfilled cavity. It fits very well for loading the MEMS- based rubidium filter cell and absorption cell for miniaturized rubidium atomic frequency standards.

Linear and nonlinear physics of the magnetoacoustic cyclotron instability of fusion-born ions in relation to ion cyclotron emission

The magnetoacoustic cyclotron instability (MCI) probably underlies observations of ion cyclotron emission (ICE) from energetic ion populations in tokamak plasmas, including fusion-born alpha-particles in JET and TFTR [Dendy et al., Nucl. Fusion 35, 1733 (1995)]. ICE is a potential diagnostic for lost alpha-particles in ITER; furthermore, the MCI is representative of a class of collective instabilities, which may result in the partial channelling of the free energy of energetic ions into radiation, and away from collisional heating of the plasma. Deep understanding of the MCI is thus of substantial practical interest for fusion, and the hybrid approximation for the plasma, where ions are treated as particles and electrons as a neutralising massless fluid, offers an attractive way forward. The hybrid simulations presented here access MCI physics that arises on timescales longer than can be addressed by fully kinetic particle-in-cell simulations and by analytical linear theory, which the present simulations largely corroborate. Our results go further than previous studies by entering into the nonlinear stage of the MCI, which shows novel features. These include stronger drive at low cyclotron harmonics, the re-energisation of the alpha-particle population, self-modulation of the phase shift between the electrostatic and electromagnetic components, and coupling between low and high frequency modes of the excited electromagnetic field.

Manipulating the excitation transfer in Photosystem I using a Fabry–Perot metal resonator with optical subwavelength dimensions

We demonstrate controlled modification of the fluorescence and energy transfer properties of Photosystem I (PSI) - one of the most important light harvesting systems - by using a newly developed approach to produce optical subwavelength microcavities for cryogenic temperature issues. The experiments were carried out on PSI from the cyanobacterium Arthrospira platensis as it shows a broad and structured fluorescence emission. By changing the distance between the cavity forming mirrors, the electromagnetic field mode structure around PSI is varied affecting the emission and energy transfer properties, which allows us to selectively enhance signals of resonant emitters and suppress off-resonant emission. By comparing the experimental data with simulations, we are able to show how excitation transfer within PSI is affected by the microcavity. The ability to control the energy transfer within such efficient energy converters as photosynthetic proteins can establish the opportunity for enhancing the efficiencies of bio-solar applications. The defined control of the resonance conditions by microcavities makes them a preferable tool to study the effects of additional electromagnetic modes on the energy transfer in any coupled multi-chromophore system. The resonator geometry excludes the direct contact of the proteins with any surface. Possible quenching or denaturation of the complexes close to metal surfaces is still an insuperable obstacle for studies with proteins and nanostructures, which can be avoided by resonators.

Bound entanglement in the Jaynes–Cummings model

We study in detail entanglement properties of the Jaynes–Cummings model assuming a two-level atom (qubit) interacting with the first N levels of an electromagnetic field mode (qudit) in a cavity. In the Jaynes–Cummings model, the number operator is the conserved quantity that allows for the exact diagonalization of the Hamiltonian and thus we study states that commute with this conserved quantity and whose structure is preserved under the Jaynes–Cummings dynamics. Contrary to the common belief, we show that there are bound entangled states that satisfy the symmetries imposed by the conservation of the number of excitations when N > 3. Furthermore we show that the Jaynes–Cummings interaction can be used to generate bound entanglement between the atom and the mode.

Spontaneous emission from radiative chiral nematic liquid crystals at the photonic band-gap edge: An investigation into the role of the density of photon states near resonance

In this article, we investigate the spontaneous emission properties of radiating molecules embedded in a chiral nematic liquid crystal, under the assumption that the electronic transition frequency is close to the photonic edge mode of the structure, i.e., at resonance. We take into account the transition broadening and the decay of electromagnetic field modes supported by the so-called "mirrorless"cavity. We employ the Jaynes-Cummings Hamiltonian to describe the electron interaction with the electromagnetic field, focusing on the mode with the diffracting polarization in the chiral nematic layer. As known in these structures, the density of photon states, calculated via the Wigner method, has distinct peaks on either side of the photonic band gap, which manifests itself as a considerable modification of the emission spectrum. We demonstrate that, near resonance, there are notable differences between the behavior of the density of states and the spontaneous emission profile of these structures. In addition, we examine in some detail the case of the logarithmic peak exhibited in the density of states in two-dimensional photonic structures and obtain analytic relations for the Lamb shift and the broadening of the atomic transition in the emission spectrum. The dynamical behavior of the atom-field system is described by a system of two first-order differential equations, solved using the Green's-function method and the Fourier transform. The emission spectra are then calculated and compared with experimental data.

Spatial Variation of Magnetotelluric Field Components in simple 2D and 3D Environments

The spatial variation of magnetotelluric field components over a buried three-dimensional conductive inhomogeneity is investigated numerically. The E-polarization mode electromagnetic field components were computed for different aspect ratios of the inhomogeneity and for different frequencies of the incident waves. The results show that as aspect ratio of the inhomogeneity is reduced the spatial variation of the electric field component Ex is reduced and that of the magnetic field component Hy is increased. Furthermore, the variation of Hy is strongly influenced by frequency as aspect ratio is reduced. Familiarity with these variations is important in understanding the behaviour of theoretically computed apparent resistivities which are useful in the interpretation of magnetotelluric field measurements for investigating geologic structures.KEYSWORDS: Spatial variation, E- polarization mode, Magnetotelluric field components, Electromagnetic field components, Three – dimensional, Two – dimensional, Aspect ratio.

Effects of nonlocal plasmons in gapped graphene micro-ribbon array and two-dimensional electron gas on near-field electromagnetic response in the deep subwavelength regime

A self-consistent theory involving Maxwell's equations and a density-matrix linear-response theory is solved for an electromagnetically coupled doped graphene micro-ribbon array (GMRA) and a quantum well (QW) electron gas sitting at an interface between a half-space of air and another half-space of a doped semiconductor substrate, which supports a surface-plasmon mode in our system. The coupling between a spatially modulated total electromagnetic (EM) field and the electron dynamics in a Dirac-cone of a graphene ribbon, as well as the coupling of the far-field specular and near-field higher-order diffraction modes, are included in the derived electron optical-response function. Full analytical expressions are obtained with nonlocality for the optical-response functions of a two-dimensional electron gas and a graphene layer with an induced bandgap, and are employed in our numerical calculations beyond the long-wavelength limit (Drude model). Both the near-field transmissivity and reflectivity spectra, as well as their dependence on different configurations of our system and on the array period, ribbon width, graphene chemical potential of QW electron gas and bandgap in graphene, are studied. Moreover, the transmitted E-field intensity distribution is calculated to demonstrate its connection to the mixing of specular and diffraction modes of the total EM field. An externally tunable EM coupling among the surface, conventional electron-gas and massless graphene intraband plasmon excitations is discovered and explained. Furthermore, a comparison is made between the dependence of the graphene-plasmon energy on the ribbon's width and chemical potential in this paper and the recent experimental observation given by [Nat. Nanotechnol.6, 630-634 (2011)] for a GMRA in the terahertz-frequency range.

Master equation and dispersive probing of a non-Markovian process

For a bosonic (fermionic) open system in a bath with many bosons (fermions) modes, we derive the exact non-Markovian master equation in which the memory effect of the bath is reflected in the time dependent decay rates. In this approach, the reduced density operator is constructed from the formal solution of the corresponding Heisenberg equations. As an application of the exact master equation, we study the active probing of non-Markovianity of the quantum dissipation of a single boson mode of electromagnetic (EM) field in a cavity QED system. The non-Markovianity of the bath of the cavity is explicitly reflected by the atomic decoherence factor.

Measurement of Vibrational Modes in SingleSiO2Nanoparticles Using a Tunable Metal Resonator with Optical Subwavelength Dimensions

Using a tunable optical subwavelength microcavity, we demonstrate controlled modification of the vibronic relaxation dynamics in a single SiO(2) nanoparticle. By varying the distance between the cavity mirrors we change the electromagnetic field mode structure around a single nanoparticle and the radiative transition probability from the lowest vibronic level of the electronically excited state to the progression of phonon levels in the electronic ground state. We demonstrate redistribution of the photoluminescence spectrum between zero-phonon and phonon-assisted bands and modification of the excited state lifetime of the same individual SiO(2) particle measured at different cavity lengths. By comparing the experimental data with a theoretical model, we extract the quantum yield of a single SiO(2) nanoparticle.

Late-time tails of fields around Schwarzschild black hole surrounded by quintessence

The evolution of scalar, electromagnetic and gravitational fields around spherically symmetric black hole surrounded by quintessence are studied with special interest on the late-time behavior. In the ring down stage of evolution, we find in the evolution picture that the fields decay more slowly due to the presence of quintessence. As the quintessence parameter \epsilon decreases, the decay of l=0 mode of scalar field gives up the power-law form of decay and relaxes to a constant residual field at asymptotically late times. The l>0 modes of scalar, electromagnetic and gravitational fields show a power-law decay for large values of \epsilon, but for smaller values of \epsilon they give way to an exponential decay.

Effect of atomic decay on purity, total correlations and entanglement of pure and mixed states

Abstract The atomic decay for a two level atom interacting with a single mode of electromagnetic field is considered. In particular for a coherent state or statistical mixture ( SM ) of two opposite coherent states as initial field states, the exact solution of the master equation is found. Effect of the atomic damping on the partial entropies of the atom or the field and the total entropy as a measures of the purity loss is investigated. The degree of entanglement by the negativity and the mutual information and the atomic coherence through the master equation is studied.

A New Broadband Microstrip-to-SIW Transition Using Parallel HMSIW

In this work, a new microstrip-to-substrate integrated waveguide (SIW) transition using the parallel half-mode substrate integrated waveguide (HMSIW) is proposed. The proposed transition consists of three sections : a microstrip, parallel HMSIWs, and an SIW. By inserting the parallel HMSIWs section between the microstrip section and the SIW section, the proposed transition can improve the return loss characteristics of the near cut-off frequency because the HMSIWs section has a lower cut-off frequency than the SIW section (8.6 GHz). The lower cut-off frequency is achieved through gradual electromagnetic field mode changes for a low reflection. The measured return loss is less than 20 dB in the of 9.1~16.28 GHz freqeuncy range for the back-to-back transition. The measured insertion loss is within 1.6 dB for the back-to-back transition. The proposed transition is expected to play an important role in wideband SIW circuits fed by a microstrip.

Microwave propagation in a graphenelike photonic crystal slab

In this paper, we investigate the transport properties of microwaves in a two-dimensional (2D) graphenelike photonic crystal (PC) slab. We realize a narrow electromagnetic (EM) beam by using a grounded coplanar waveguide with better direction, which is beneficial to the study of the transport properties of (2D) PCs. The extremal transmission of the microwave near the Dirac point in a graphenelike PC slab, being inversely proportional to the thickness of the sample, is demonstrated by means of numerical simulation. Furthermore, we verify experimentally that some certain EM field modes for photonic bands cannot be excited in the PC slab.

Optical Fiber-Based Surface-Enhanced Raman Scattering Sensor Using Au Nanovoid Arrays

Plasmonic properties of gold nanovoid array substrates for fiber-based surface-enhanced Raman scattering (SERS) sensing are studied numerically and experimentally. In the nanovoid arrays, each void has openings on both sides, bottom hole facing the fiber tip for introducing incident light and collecting scattered light and the top hole exposed to the analyte solution for interrogating analyte molecules in the voids. Electromagnetic field modes are confined strongly in and around these nanovoids, acting as localized plasmon resonators. The enhanced electric field extends hundreds of nanometers into the voids, resulting in a large SERS-active zone several orders of magnitude larger than nanoparticle-based structures. The effect of structural parameters of the nanovoid arrays, including void diameter, Au film thickness, and bottom hole diameter, on electric field confinement in the voids is investigated using three-dimensional finite difference time domain simulation. Au nanovoid arrays are fabricated using a scalable, inexpensive nanosphere lithography fabrication method. The largest SERS signal is realized by tuning the localized plasmon resonance peak of Au nanovoid arrays to the laser excitation wavelength. Multiplexed detection capability with the fiber-based SERS sensor using Au nanovoid arrays is demonstrated by measuring the Raman spectrum of a mixture solution of diethylthiatricarbocyanine and crystal violet.