Poynting Vector Analysis Research Articles

Observations of co-existing rising and falling tone emissions of electromagnetic ion cyclotron waves

We report observations of co-existing rising and falling tone emissions of electromagnetic ion cyclotron (EMIC) waves by THEMIS E spacecraft. The investigation of these fine structures of the EMIC waves is essential from the point of view of understanding the connection between the proton holes and the proton hills in velocity phase-space. The wave packets of rising and falling tones are tracked by Poynting vector analysis, where we observe that the rising tones are propagating northward and the falling tones are propagating southward. The nonlinear wave growth theory supports our observations. We propose a model where the proton velocity distribution function evolves through the formation of proton holes on the negative side of the distribution function and mirrored resonant protons forming proton hills on the positive side of the distribution function, allowing us to observe the co-existing rising and falling tone EMIC waves.Graphical abstract

Tailoring the directional dependent emitter interaction based plasmonic antenna character of Ag–Au heterodimer

Based on the concept of optical nanoantennas, light-matter interaction between metal heterodimer (Ag and Au spherical nanoparticles) and single dipole emitter system are numerically simulated utilizing a MATLAB toolbox MNPBEM17 based on boundary element method (BEM). The precise position and orientation of the dipole emitter systematically controls not only the (non)radiative losses, but also the efficiency of excitation (absorption) and respective emission processes in the vicinity of the plasmonic optical antenna system. The overall (non)radiative decay rates and associated surface charge distributions help estimate the spatio-directional dependency of dipole emitter emission, analogous to that of the SERS enhancement. Furthermore, the Poynting vector analysis of our present hybrid plasmonic antenna system effectively assesses the flow of electromagnetic energy, thus accounting for improvement in both near- and far-field propagation modes. The calculation of Purcell factor and coupling strength along with quantum yield evaluate the detailed optical response of a nanoantenna characteristics simultaneously based on the dipole emitter position and orientation, offering better scope for understanding the underlying mechanisms governing such intriguing interactions in complex geometries as well.

Near-Field Light-Bending Photonic Switch: Physics of Switching Based on Three-Dimensional Poynting Vector Analysis

Photonic hook is a high-intensity, bent light focus with a proportional curvature to the wavelength of the incident light. Based on this unique light-bending phenomenon, a novel near-field photonic switch by means of a right-trapezoid dielectric Janus particle-lens embedded in the core of a planar waveguide is proposed for switching the photonic signals at two common optical communication wavelengths, 1310 nm and 1550 nm, by using numerical simulations. The signals at these two wavelengths can be guided to different routes according to their oppositely bent photonic hooks to realise wavelength selective switching. The switching mechanism is analysed by an in-house developed three-dimensional (3D) Poynting vector visualisation technology. It demonstrates that the 3D distribution and number of Poynting vector vortexes produced by the particle highly affect the shapes and bending directions of the photonic hooks causing the near-field switching, and multiple independent high-magnitude areas matched by the regional Poynting vector streamlines can form these photonic hooks. The corresponding mechanism can only be represented by 3D Poynting vector distributions and is being reported for the first time.

Design methodology of a surface plasmon resonance-based affinity biosensor using instantaneous Poynting vector analysis

We deduce mathematical equations for instantaneous optical power density (instantaneous Poynting vector) of three-layer lossy optical waveguide consisting of metal-dielectric interfaces. We propose new equations which can be exploited to compute the thicknesses and refractive indices of various optical layers engaged in the evanescently coupled optical and nano-photonic devices. We then propose the design of a plasmonic sensor to be used in the detection of biological entities such as the concentration of a specific bacteria E. coli. We then use the new equations to determine the best value of the thickness of the dielectric layer to be used as the affinity layer for immobilizing the specific bacteria population on the surface of the sensor, which in our sensor design is taken to be silica, and examine its performance. Thereafter we discuss how to apply our derived equations to determine the best thickness of a thin dielectric layer (having high value of its refractive index) that can be added into any traditional SPR-based sensor to improve its sensitivity and other parameters. The calculated best values of the thickness of the dielectric is seen to be highly correlated with previously published experimental data by other researchers.

Broadband microwave absorber composed of sandwich structure with a lossless medium as the intermediate layer

A broadband microwave absorber with a sandwich structure has been designed, creatively taking lossless medium (paraffin or air) as the intermediate layer. The paraffin layer effectively adjusted the impedance of the absorber, especially at the high-frequency region, hence observably raising the upper limit of the effective absorption region from 14.5 GHz to 18 GHz. As a result, the effective absorption bandwidth (EAB, reflection loss less than −10 dB) is broadened to 10.1 GHz, covering the entire Ku band and the entire X band, with a total thickness of only 2.5 mm, among which the paraffin intermediate layer has a thickness of 0.8 mm. Based on Maxwell's equations, normalized Poynting vector and loss analysis are given, which reveals the paraffin layer can enhance the total loss, though paraffin is lossless. In addition, the intermediate paraffin layer can also be replaced with air or even vacuum, providing a new perspective for the design of a high-performance absorber with lighter weight.

Investigation of reactive power distribution between two coils of inductive power transfer system by Poynting vector analysis

It is well known that real power can be transferred through the air gap between two coupled coils in an Inductive Power Transfer (IPT) system, but little is known about how the reactive power spatially circulates in the airgap between the coils. This paper investigates the reactive power distribution in an IPT system from the field point of view. The Magnetic field, electric field and resultant Poynting vector at an arbitrary point between two coupled coils are analysed by fundamental electromagnetic equations. In particular, the reactive power distribution is investigated under both open-circuit and loaded conditions. The measured results at the input and output of the two coupled coils show a good agreement with the Poynting vector and lumped circuit analysis. Furthermore, the Poynting vector analysis shows that the two mutual components of the Poynting vector contribute to reactive power circulation between the two coupled coils, while the self-components only affect the generation of reactive power around the individual coil. These results cannot be obtained by numerical or traditional lumped circuit analysis, and they are very useful for understanding the deep-level physical power transfer mechanism of an IPT system.

Performance optimization of bi-metallic surface plasmon resonance based sensors with silicon layer using poynting vector analysis

Performance optimization of bi-metallic surface plasmon resonance based sensors with silicon layer using poynting vector analysis

Study of power flow mechanism of capacitive power transfer system based on Poynting vector analysis

In this paper, the power flow mechanism of a typical Capacitive Power Transfer (CPT) system is studied by analysing the electric field, magnetic field, and Poynting vector, to determine the power distribution as well as the average power flow to the load. It is found that the average power from the source flows along the wires on the transmitting side and passes the external areas of the coupling plates mainly along the channel between the two coupling pairs (instead of going through the air gaps in between), then converges along the wires before reaching the load. The average power calculated by integrating the real part of the Poynting vector across a defined power flow plane at the receiving end is consistent with CST (Computer Simulation Technology) simulation, circuit analysis, and practical measurements of the CPT system. Although the power density described by Poynting vector changes with the separation distance between the two coupling pairs, the total average power keeps approximately constant because the power flow area changes accordingly. Compared to the traditional lumped circuit analysis, the Poynting vector analysis shows the power distribution around the coupling plates in relation to their physical configuration. This research reveals the power flow mechanism and distribution in a CPT system from field point of view, which is useful to gain deeper understanding of the CPT system beyond the traditional circuit theory and would also be helpful to improve practical system design in the future.

Bidirectional reflectance distribution function algorithm based on the Poynting vector analysis

We used Maxwell’s partial differential equations of electrodynamics to quantify radiation and scattering on rough surfaces. The electrical field and the magnetic field are the results from the near-field. To find the bidirectional reflectance distribution function (BRDF) of the far-field, we present an algorithm for BRDF based on near-to-far-field projection and Poynting vector analysis. This algorithm accounts for characteristics of the BRDF function, focuses on the Poynting vector of the outgoing radiation, and creates a virtual projection surface to serve for the BRDF. The near-field data are recorded on a rectangular shape, and the far-field data are recorded on a virtual hemispherical surface. The BRDF can be calculated using Green’s theorem for the selected area on the virtual hemispherical surface. The results show that, for RMS 0.1 to 0.5 μm, the incident wavelengths are 400 to 700 nm, the surface roughness ranges from smooth to slightly rough, the simulation agrees with the scattering theory, and the accuracy of the algorithm is significantly higher than that of the Cook–Torrance BRDF model.

Theoretical Modeling of the Internal Power Flow and Absorption Loss of the Air Mode Based on the Proposed Poynting Vector Analysis in Top-emitting Organic Light-emitting Diodes

We propose the Poynting vector analysis of the air mode in a top-emitting organic light-emitting diode (OLED) by combining the transfer matrix method and dipole source term. The spatial profiles of the time-averaged optical power flow of the air mode are calculated inside and outside the multilayer structure of the OLED with respect to the thickness of the semi-transparent top cathode and capping layer (CPL). We elucidate how the micro-cavity effect controlled by the thickness variation of the semi-transparent top cathode or CPL affects the internal optical power and absorption loss inside the OLED multilayer and the external optical power coupled into the air. When the calculated absorption loss and external power obtained by the proposed Poynting vector and currently-used point dipole models are compared, two calculation results are identical, which demonstrates the validity of the two models.

Highly efficient coupler for dielectric slot waveguides and hybrid plasmonic waveguides

A compact, highly efficient optical coupler for dielectric slot waveguides and hybrid plasmonic waveguides based on transition layers (air slot grooves) was investigated. The power-coupling efficiency of 75% for the direct coupling case increased to 90% following the insertion of an intermediate section. By performing time-averaged Poynting vector analysis, we successfully separated the factors of transmission, reflection, and radiation at the coupler interface. We found that the insertion of optimal air grooves into the coupler structure contributed to the improvement of coupling performance. The proposed compact structure is characterized by a high transmission efficiency, low reflection, small length, and broad-band spectrum response.

Study of Power Flow in an IPT System Based on Poynting Vector Analysis

This paper analyzes the power distribution and flow of an inductive power transfer (IPT) system with two coupled coils by using the Poynting vector. The system is modelled with a current source flowing through the primary coil, and a uniformly loaded secondary first, then the Poynting vector at an arbitrary point is analyzed by calculating the magnetic and electric fields between and around of the two coils. Both analytical analysis and numerical analysis have been undertaken to show the power distribution, and it has found that power distributes as a donut shape in three-dimensional (3D) space and concentrates along the edges in the proposed two-coil setup, instead of locating coaxially along the center path. Furthermore, power flow across the mid-plane between the two coils is analyzed analytically by the surface integral of the Poynting vector, which is compared with the input power from the primary and the output power to the secondary coil via coupled circuit theory. It has shown that for a lossless IPT system, the power transferred across the mid-plane is equal to the input and output power, which validates the Poynting vector approach. The proposed Poynting vector method provides an effective way to analyze the power distribution in the medium between two coupled coils, which cannot be achieved by traditional lumped circuit theories.

A relook at radiation by a point charge. I

Efforts to suggest a classical model for the hydrogen atom are discouraged by a conclusion, based on the principles of electrodynamics, that an accelerating charged particle necessarily radiates. In this paper, we re-examine the steps leading to this conclusion. We start with the relativistic expressions for energy and momentum of a particle and establish the relationship between special relativity and electrodynamics. The standard field expression and its relativistic transformations are then studied for a point charge source, represented by a delta function. In conventional Poynting’s theorem analysis, the rate of change of work done on a system of charges is written as addition of two terms, rate of change of stored energy, and surface integral of Poynting vector. For a delta function source, the first two terms of this equation are either non-integrable or difficult to evaluate. Only the third surface integration term can be evaluated, which is said to give radiation by the point charge. Thus, the statement that an accelerated charge radiates is a conclusion based on this Poynting vector analysis. We examine it and realize that this statement, namely, that a point charge radiates continuously just because it is accelerating, does not have adequate theoretical justification.

Poynting vector analysis for wireless power transfer between magnetically coupled coils with different loads

Wireless power transfer is a nonradiative type of transmission that is performed in the near-field region. In this region, the electromagnetic fields that are produced by both the transmitting and receiving coils are evanescent fields, which should not transmit energy. This then raises the question of how the energy can be transferred. Here we describe a theoretical study of the two evanescent field distributions at different terminal loads. It is shown that the essential principle of wireless energy transfer is the superposition of the two evanescent fields, and the resulting superimposed field is mediated through the terminal load. If the terminal load is either capacitive or inductive, then the superimposed field cannot transfer the energy because its Poynting vector is zero; in contrast, if the load is resistive, energy can then be conveyed from the transmitting coil to the receiving coil. The simulation results for the magnetic field distributions and the time-domain current waveforms agree very well with the results of the theoretical analysis. This work thus provides a comprehensive understanding of the energy transfer mechanism involved in the magnetic resonant coupling system.

Development of Visible Light Absorption Measurement for Concentrated Dye Solution based on Attenuated Total Reflection Technique and Improvement on its Analysis Method

An absorption measurement working in ATR (Attenuated Total Reflection) mode has been design for characterization of concentrate dye solution. The system consists of a visible light system as polychromatic wave source, an ATR plate made up from glass or polymer, a spectrometer with a CCD detector. The system is connected to a computer for measurement and data processing. Some commercial inks measured by this ATR system showed absorption spectra which are in agreement with the color of the inks. The absorption parameter will be determined from the incident and reflection beam intensities measured at incident angle larger than the critical angle. We have also carried out Poynting vector analysis and we will show that the energy flow in the normal direction of the interface is not zero. The energy flow, however, decreases along the normal direction of the interface, indicating energy loss due to light absorption in the sample medium. The amount of energy loss depends on the attenuation index or absorption parameters, which is important for formulating the relation between the measured intensities and absorption parameters.

Simulation of GaN-Based Light-Emitting Diodes With Hemisphere Patterned Sapphire Substrate Based on Poynting Vector Analysis

The GaN-based light-emitting diodes (LEDs) with hemisphere patterned sapphire substrate (PSS) have been investigated numerically using a combined method of ray tracing and finite-difference time-domain techniques based on Poynting vector. Our method has been verified using unpatterned sapphire substrate for which analytical formulas exist. The simulated results show that the hemisphere PSS can improve the light extraction efficiency by increasing the reflection angle, decreasing the transmission angle, enhancing the reflectance of light incident on it, and enlarging the escape cone at its interface. Moreover, it is found that the hemisphere pattern size has significant influence on the improvement of the LED emission efficiency. The optimal radius of the hemisphere is about the emission wavelength of GaN-based LEDs, which can be attributed to the strong effect of wave properties of light at the PSS interface.

Influence of losses on the superresolution performances of an impedance-matched negative-index material

We discuss by a Poynting vector analysis how the losses of a negative-index material (NIM) affect the resolution performances of a Veselago-Pendry lens, and we analyze those performances in the framework of the Abbe criterion. The limits of both high losses and low losses are explored. We find that the impedance-matched NIM is able to resolve 30% better than the limit imposed by the Abbe criterion even when the imaginary part of the refractive index (the material losses) exceeds the absolute value of the real part of the refractive index. The NIM is described by a lossy Drude model with equal permittivity and permeability. By increasing the damping parameter of the Drude model, we also explore the regime where both permittivity and permeability are positive and point out the conditions under which the metamaterial is still able to superresolve.

Poynting vector analysis of a superlens

A power analysis of the lossy negative refractive index or left-handed slab lens is described. The presence of vortices in the image plane is revealed with small loss or gain, and these are attributed to the influence of field growth in the evanescent spectrum.

Telegrapher equations for arbitrary frequencies and modes: Radiation of an infinite, lossless transmission line

Maxwell's equations for an infinite, lossless transmission line above a perfectly conducting ground are transformed into telegrapher equations with new generalized per‐unit‐length parameters of the conductor. These new line parameters are complex‐valued, frequency‐dependent, and contain the radiation resistance. Their explicit expressions depend on the chosen gauge, but there is also a gauge‐independent representation for them. In the quasi‐static approach of the Maxwell‐Telegrapher equations the line parameters become real‐valued, and radiation is absent. A Poynting vector analysis leads to a deeper physical understanding and interpretation of the new parameters.

Design of Multilayer Planar Transmission Lines by Generalized Spectral-Domain Immitance Approach

ABSTRACT A variety of multilayer planar transmission lines are analyzed by the generalized spectral-domain immitance approach. The three-directional electromagnetic-field Green's functions excited by horizontal electric currents/fields are analytically derived for a multilayer planar structure. With these explicit field expressions, the planar transmission lines, such as microstrip lines, coplanar waveguides (CPW's) with/without backed conductor, are characterized. Rigorous Poynting vector analysis is utilized to calculate the propagated powers of the fundamental and higher-order modes. According to the propagated power distribution, design considerations for planar transmission lines are discussed. A slightly lossy conductor-backed CPW is proposed to attenuate the unwanted even-mode propagation and to maintain a low loss of the desired CPW odd-mode propagation.