Relevant Electromagnetic Fields Research Articles

Engineering nonlinear optical phenomena by arbitrarily manipulating the phase relationships among the relevant optical fields

Nonlinear optical processes are intrinsically dominated by the phase relationships among the relevant electromagnetic fields, including the phase of nonlinear polarization produced in them. If one can arbitrarily manipulate these phase relationships at a variety of desired interaction lengths, direct and highly designable manipulations for the nonlinear optical phenomenon could be achieved. Here, we report a proof-of-principle experiment in which a high-order Raman-resonant four-wave-mixing process is used as a representative nonlinear optical process and is tailored to a variety of targets by implementing such arbitrary manipulations of the phase relationships in the nonlinear optical process. We show that the output energy is accumulated to a specific, intentionally selected Raman mode on demand; and at the opposite extreme, we can also distribute the output energy equally over broad high-order Raman modes in the form of a frequency comb. This concept in nonlinear optical processes enables an attractive optical technology: a single-frequency tunable laser broadly covering the vacuum ultraviolet region, which will pave the way to frontiers in atomic-molecular-optical physics in the vacuum ultraviolet region.

Qualia and Phenomenal Consciousness Arise From the Information Structure of an Electromagnetic Field in the Brain.

In this paper we address the following problems and provide realistic answers to them: (1) What could be the physical substrate for subjective, phenomenal, consciousness (P-consciousness)? Our answer: the electromagnetic (EM) field generated by the movement and changes of electrical charges in the brain. (2) Is this substrate generated in some particular part of the brains of conscious entities or does it comprise the entirety of the brain/body? Our answer: a part of the thalamus in mammals, and homologous parts of other brains generates the critical EM field. (3) From whence arise the qualia experienced in P-consciousness? Our answer, the relevant EM field is “structured” by emulating in the brain the information in EM fields arising from both external (the environment) and internal (the body) sources. (4) What differentiates the P-conscious EM field from other EM fields, e.g., the flux of photons scattered from object surfaces, the EM field of an electro-magnet, or the EM fields generated in the brain that do not enter P-consciousness, such as those generated in the retina or occipital cortex, or those generated in brain areas that guide behavior through visual information in persons exhibiting “blindsight”? Our answer: living systems express a boundary between themselves and the environment, requiring them to model (coarsely emulate) information from their environment in order to control through actions, to the extent possible, the vast sea of variety in which they are immersed. This model, expressed in an EM field, is P-consciousness. The model is the best possible representation of the moment-to-moment niche-relevant (action-relevant: affordance) information an organism can generate (a Gestalt). Information that is at a lower level than niche-relevant, such as the unanalyzed retinal vector-field, is not represented in P-consciousness because it is not niche-relevant. Living organisms have sensory and other systems that have evolved to supply such information, albeit in a coarse form.

Tailored Raman-resonant four-wave-mixing processes.

Nonlinear optical processes are strongly dominated by phase relationships among electromagnetic fields involved. In this paper, we theoretically and experimentally show that in a Raman-resonant four-wave-mixing process, the first anti-Stokes and Stokes generations can be tailored in a variety of ways by manipulating the phase relationships among the relevant electromagnetic fields.

On the dipole approximation with error estimates

The dipole approximation is employed to describe interactions between atoms and radiation. It essentially consists of neglecting the spatial variation of the external field over the atom. Heuristically, this is justified by arguing that the wavelength is considerably larger than the atomic length scale, which holds under usual experimental conditions. We prove the dipole approximation in the limit of infinite wavelengths compared to the atomic length scale and estimate the rate of convergence. Our results include N-body Coulomb potentials and experimentally relevant electromagnetic fields such as plane waves and laser pulses.

Coil Design and Measurements of Automotive Magnetic Resonant Wireless Charging System for High-Efficiency and Low Magnetic Field Leakage

For wireless charging of electric vehicle (EV) batteries, high-frequency magnetic fields are generated from magnetically coupled coils. The large air-gap between two coils may cause high leakage of magnetic fields and it may also lower the power transfer efficiency (PTE). For the first time, in this paper, we propose a new set of coil design formulas for high-efficiency and low harmonic currents and a new design procedure for low leakage of magnetic fields for high-power wireless power transfer (WPT) system. Based on the proposed design procedure, a pair of magnetically coupled coils with magnetic field shielding for a 1-kW-class golf-cart WPT system is optimized via finite-element simulation and the proposed design formulas. We built a 1-kW-class wireless EV charging system for practical measurements of the PTE, the magnetic field strength around the golf cart, and voltage/current spectrums. The fabricated system has achieved a PTE of 96% at the operating frequency of 20.15 kHz with a 156-mm air gap between the coils. At the same time, the highest magnetic field strength measured around the golf cart is 19.8 mG, which is far below the relevant electromagnetic field safety guidelines (ICNIRP 1998/2010). In addition, the third harmonic component of the measured magnetic field is 39 dB lower than the fundamental component. These practical measurement results prove the effectiveness of the proposed coil design formulas and procedure of a WPT system for high-efficiency and low magnetic field leakage.

Freely designable optical frequency conversion in Raman-resonant four-wave-mixing process.

Nonlinear optical processes are governed by the relative-phase relationships among the relevant electromagnetic fields in these processes. In this Report, we describe the physics of arbitrary manipulation of Raman-resonant four-wave-mixing process by artificial control of relative phases. As a typical example, we show freely designable optical-frequency conversions to extreme spectral regions, mid-infrared and vacuum-ultraviolet, with near-unity quantum efficiencies. Furthermore, we show that such optical-frequency conversions can be realized by using a surprisingly simple technology where transparent plates are placed in a nonlinear optical medium and their positions and thicknesses are adjusted precisely. In a numerical simulation assuming practically applicable parameters in detail, we demonstrate a single-frequency tunable laser that covers the whole vacuum-ultraviolet spectral range of 120 to 200 nm.

Analytical Expressions for Electromagnetic Fields Associated with the Inclined Lightning Channels in the Time Domain

This article describes general analytical equations that are developed for the calculation of electromagnetic fields due to an inclined channel directly in the time domain. The input parameters of the model, angle of inclination of the lightning channel and the angle at the observation point can be varied through all possible values to produce the relevant electromagnetic fields. The proposed model is validated with eight electromagnetic waveforms measured at close range of the lightning channel. The results of the model show good agreement with the measured data. Furthermore, the proposed equations are compatible with different channel base current functions. The equations could easily be applied in the coupling models that calculate induced voltages in conductors in the presence of lightning-generated electromagnetic fields.

The electromagnetics of light transmission through subwavelength slits in metallic films

By numerically calculating the relevant electromagnetic fields and charge current densities, we show how local charges and currents near subwavelength structures govern light transmission through subwavelength apertures in a real metal film. The illumination of a single aperture generates surface waves; and in the case of slits, generates them with high efficiency and with a phase close to -π with respect to a reference standing wave established at the metal film front facet. This phase shift is due to the direction of induced charge currents running within the slit walls. The surface waves on the entrance facet interfere with the standing wave. This interference controls the profile of the transmission through slit pairs as a function of their separation. We compare the calculated transmission profile for a two-slit array to simple interference models and measurements [Phys. Rev. B 77(11), 115411 (2008)].

A quasi-static model for the ring capacitor applicator

The electromagnetic heat dissipation in a radially layered biological tissue inside a ring capacitor (RC) applicator has been investigated. A quasi-static model is introduced to compute the relevant electromagnetic field quantities. The method of computation employs the spatial Fourier transform of all field quantities with respect to the axial coordinate. After an iterative solution of a dual boundary value problem for the electric potential and the current density at the electrodes, an inverse Fourier transform is carried out to compute the quantities that are of interest to the deep-body system at hand. Comparison of numerical results with phantom measurements shows excellent agreement.

Modulation of endothelial cell proliferation and differentiation responses by a clinically relevant pulsed electromagnetic field

Modulation of endothelial cell proliferation and differentiation responses by a clinically relevant pulsed electromagnetic field

Reflection and transmission characteristics of a slab with periodically varying surfaces

Using a plane wave spectral decomposition of the relevant electromagnetic (EM) fields and the T-matrix solution philosophy, a T-matrix is formulated which completely characterizes the EM response of an infinite material plate bounded by two homogeneous half-spaces, the two interfaces being periodically rough. Individual T-matrices for either of the two periodic bimaterial interfaces are used in this derivation. Using the computed results, the anomalies in the scattering response of the rough slab are explained in terms of reflectionless and transmissionless modes, the Brewster angle, and the conditions for propagation or evanescence of a given plane wave mode.