Larry Velasco

Negative Refraction in Perspective

The concept of negative refraction is attracting a lot of attention. The initial ideas and the misconceptions that have arisen are discussed in sufficient detail to understand the conceptual structure that binds negative refraction to the existence of backward wave and forward wave phenomena. A presentation of the properties of isotropic media supporting backward waves is followed by a discussion of negative phase velocity media, causality, anisotropic crystals, and some connections to photonic crystals. The historical background is always coupled to a detailed presentation of all the issues. The paper is driven numerically and is illustrated with the outcomes of original FDTD simulations.

Gyrotropic impact upon negatively refracting surfaces

Surface wave propagation at the interface between different types of gyrotropic materials and an isotropic negatively refracting medium, in which the relative permittivity and relative permeability are, simultaneously, negative is investigated. A general approach is taken that embraces both gyroelectric and gyromagnetic materials, permitting the possibility of operating in either the low GHz, THz or the optical frequency regimes. The classical transverse Voigt configuration is adopted and a complete analysis of non-reciprocal surface wave dispersion is presented. The impact of the surface polariton modes upon the reflection of both plane waves and beams is discussed in terms of resonances and an example of the influence upon the Goos–Hanchen shift is given.

Gyroelectric cubic-quintic dissipative solitons

The influence of an externally applied magnetic field upon classic cubic quintic dissipative solitons is investigated using both exact simulations and a Lagrangian technique. The basic approach is to use a spatially inhomogeneous magnetic field and to consider two important geometries, namely the Voigt and the Faraday effects. A layered structure is selected for the Voigt case, with the principal aim being to demonstrate nonreciprocal behavior for various classes of spatial solitons that are known to exist as solutions of the complex Ginzburg-Landau cubic-quintic envelope equation under dissipative conditions. The system is viewed as dynamical, and we display the behavior patterns of the spatial solitons in terms of two-dimensional dynamical plots involving the total energy and the peak amplitude of the spatial solitons. This leads to limit cycle plots that beautifully reveal the behavior of the solitons solutions at all points along the propagation axis. The closed contour that exists in the absence of a magnetic field is opened up, and a limit point is exposed. The onset of chaos is revealed in a dramatic way, and it is clear that detailed control by the external magnetic field can be exercised. The Lagrangian approach is adjusted to deal with dissipative systems, and through the choice of particular trial functions, aspects of the dynamic behavior of the spatial are predicted by this approach. Finally, some vortex dynamics in the Faraday configuration are investigated.

Excitation of vortices using linear and nonlinear magnetostatic waves.

It is shown that stationary vortex structures can be excited in a ferrite film, in the important centimeter and millimeter wavelength ranges. It is shown that both linear and nonlinear structures can be excited using a three-beam interaction created with circular antennas. These give rise to a special phase distribution created by linear and nonlinear mixing. An interesting set of three clockwise rotating vortices joined by one counter-rotating one presents itself in the linear regime: a scenario that is only qualitatively changed by the onset of nonlinearity. It is pointed out that control of the vortex structure, through parametric coupling, based upon a microwave resonator, is possible and that there are many interesting possibilities for applications.

Bright spatial solitons, nonlinear guided waves, and complex metamaterial structures

The creation of electromagnetic metamaterials is an important activity. The latter should anticipate the kind of applications in which unique metamaterial behaviour can appear. This paper addresses nonlinear wave phenomena in both the strongly and the weakly nonlinear regimes. It inevitably involves novel nonlinear guided waves and solitonic beam activities. In this context, some magnetooptic control is introduced. In addition, the kind of structural complexity that can lead to trapped rainbows will be briefly examined. Finally, some aspects are made of vortex control in a diffraction-managed metamaterial is presented.

Modeling and Theory of Nonlinear or Gyrotropic Negative Phase Velocity Metamaterials

Negative phase velocity metamaterials are engineered media that are currently enjoying a surge of interest due to their interesting properties and potential applications, such as cloaking to make things invisible. The literature is alive with papers devoted to the design of suitable metamaterials and there is a particular desire to create photonic applications that will operate at THz frequencies and above. At one level, the modeling of curious artificial molecules is straightforward. Nevertheless, the approximations involved need to be able to inspire confidence for optical frequency operation. Nonlinear behaviour is intrinsic to the Holy Grail quest for power control but this topic is only just being explored. With the introduction of power come the possibility of competition with damping, gain and the creation of auto- or dissipative solitons. Functionality comes not only through power control, however, but also through other externally imposed influences such as gyromagnetic effects and external stresses. Some novel possibilities that embrace these will be presented and a new generalized theory of metamaterial behaviour, based upon a nonlinear Lorentz lemma will be outlined. The outcomes of extensive computations will be used, throughout, to illustrate all the concepts in a dramatic fashion

Modeling and theory involving metamaterial photonic structures

The literature is alive with papers devoted to the design of metamaterials and there appears to be a particular desire to create photonic applications that will operate at THz frequencies and above. At one level the modelling of suitable artificial molecules is straightforward but nevertheless the approximations involved need to be able to inspire confidence for optical frequency operation. This presentation will set out a modelling activity that is known to be satisfactory only over certain frequency ranges. Split-ring and omega particles will be specifically investigated and the possibilities discovered will be related to the current experimental expertise. The detailed manner in which the constitutive relations can be controlled and the novel way in which an envelope equation emerges for even the most complex structure is exposed. The transmission and reflection properties of nano-structured materials will be discussed within a magneto-optic environment. Simulations of sub-wavelength transmission through holes in metallic and magneto-optic screens will be discussed using finite-difference time-domain (FDTD) methods. Modelling the interaction of light beams with metamaterials is developed, again using FDTD techniques, and it is shown that special care needs to be taken with structures that have sharp external edges. Finally, a summary of the problems surrounding efficient computations will be shown and some discussion of the role of genetic algorithms in metamaterial design will be featured.

Gyrotropic control of negative phase velocity media

A description of the fascinating coupling between gyrotropic media and negative refracting media will be presented. The article will address negative phase velocity media and particular types of dielectric-gyrotropic film-dielectric systems in which the applied magnetic field may result in a magneto-optic, or gyromagnetic, influence. The control features use a diverse family of dispersion curves.

Magneto-optics: applied complexity (Critical Review Lecture)

A brief review is developed of the manner in which forced gyrotropic effects can be exploited through the application of a magnetic field to special classes of materials. Magnetooptics brings controlled complexity into important two- and threedimensional phenomena. These are addressed through the introduction of dissipative-external energy input effects and optical singularities. The latter create edge and screw dislocations with latter being identified with optical vortices. The way in which magnetization distributions control vortex dynamics is discussed.