Wireless power transfer system rigid to tissue characteristics using metamaterial inspired geometry for biomedical implant applications.

Conventional resonant inductive coupling wireless power transfer (WPT) systems encounter performance degradation while energizing biomedical implants. This degradation results from the dielectric and conductive characteristics of the tissue, which cause increased radiation and conduction losses, respectively. Moreover, the proximity of a resonator to the high permittivity tissue causes a change in its operating frequency if misalignment occurs.

Generalized tensor FDTD method for sloped dispersive interfaces and thin sheets.

We present a modified formulation of the Finite-Difference Time-Domain (FDTD) technique that facilitates the accurate modeling of curved plasmonic interfaces. These interfaces appear in structures of interest for the design of optical metamaterials, such as arrays of plasmonic nanorods. Our approach uses the standard rectangular FDTD mesh and tensor effective permittivities for the interface cells, implicitly enforcing field boundary conditions, and is readily applicable to thin curved dispersive layers.

Acoustic precursor wave propagation in viscoelastic media.

Precursor field theory has been developed to describe the dynamics of electromagnetic field evolution in causally attenuative and dispersive media. In Debye dielectrics, the so-called Brillouin precursor exhibits an algebraic attenuation rate that makes it an ideal pulse waveform for communication, sensing, and imaging applications. Inspired by these studies in the electromagnetic domain, the present paper explores the propagation of acoustic precursors in dispersive media, with emphasis on biological media.

Metascreen-based superdirective antenna in the optical frequency regime.

A metascreen designed to achieve near-field subwavelength focusing at a given frequency is shown to operate as a superdirective antenna in the vicinity of that frequency at the far field. A metascreen for microwave frequencies based on a simple perfect electrically conducting screen is initially used to explain the principle of operation as a superdirective antenna and to distinguish this operation mode from that resulting in near-field subwavelength focusing. A similar metascreen design based on a silver screen of a finite thickness is then used to demonstrate superdirectivity with nanoantennas in the optical frequency regime.

Asymptotic description of wave propagation in an active Lorentzian medium.

In a causally dispersive medium the signal arrival appears in the dynamical field evolution as an increase in the field amplitude from that of the precursor fields to that of the steady-state signal. The interrelated effects of phase dispersion and frequency dependent attenuation and/or amplification alter the pulse in such a fundamental way that results in the appearance of precursor fields. Although superluminal group velocities have been found in various dispersive media, the pulse "front" and associated precursors will never travel faster than c , and hence these are the vehicles through which relativistic causality is preserved.

Joint time-frequency and finite-difference time-domain analysis of precursor fields in dispersive media.

Superluminal group velocities, defined as group velocities exceeding the speed of light in vacuum, c, have been theoretically predicted and experimentally observed in various types of dispersive media, such as passive and active Lorentzian media, one-dimensional photonic crystals, and undersized waveguides. Though superluminal group velocities have been found in these media, it has been suggested that the pulse "front" and associated transient field oscillations, known as the precursors or forerunners, will never travel faster than c, and hence relativistic causality is always preserved. Until now, few rigorous studies of these transient fields in structures exhibiting superluminal group velocities have been performed.