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Gradient-index (GRIN) optics has seen a surge of interest due to the advent of Transformation Optics (TO) which has enabled a new generation of GRIN devices. Moreover, these devices often have better performance than what has been achieved with more traditional GRIN design techniques. In order to better understand the origins of this performance improvement, such TO-derived solutions are decomposed...
Transformation optics is applied to interpret the dispersive nature of materials via changes in geometry, providing an alternative methodology for dispersion correction. An example is proposed and analyzed to demonstrate the effectiveness of the proposed technique.
A low-frequency coupling model consisting of a multi-conductor transmission line (TL) system and a small circular loop antenna is presented. The TL system is composed of N perfect electrical conductor (PEC) wires above a lossy ground. An approximate and computationally efficient analytical method is proposed to predict the current distribution on each wire. The total electromagnetic (EM) fields produced...
A low-frequency coupling model from a small circular loop antenna to a multi-conductor transmission line (TL) system composed of N perfect electric conductor (PEC) wires above a PEC ground is presented. The telegrapher's equations for the model are presented, and a computationally efficient analytical solution for the induced current distributions is formulated for each wire. An example is constructed...
The advent of Transformation Optics (TO) has led to a resurgence of interest in gradient-index (GRIN) optics. Furthermore, it has been noted that TO-derived lenses often possess better performance than those arrived at through more traditional GRIN design techniques. Due to the dispersive nature of optical materials, lenses are often combined into achromatic pairs to correct for chromatic aberrations...
An analytical method based on paraxial ray-tracing equations is proposed for designing gradient-index (GRIN) metamaterial lenses with dispersion-correction. An instructive example is considered to demonstrate the effectiveness.
A metamaterial reflector antenna is designed for robustness under high-power operating conditions by synthesizing pixelized metasurface geometries with minimized maximum field enhancement factor (MFEF) using a binary genetic algorithm (GA) stochastic optimizer. A metric is also included in the optimization to select unit cell geometries that share a high similarity among one another in order to improve...
One of the benefits of using a multi-objective algorithm is that the tradeoffs between objectives for a given design can be easily visualized. In the study of gradient-index optics, this ability can lead to a better understanding of the tradeoffs between the gradient magnitude, Δn, focus quality, and size of the optic. A gradient-index plano-convex lens is proposed to highlight the limitations of...
Metamaterial emitters have previously been studied for controlling the angle and polarization of near-IR emissivity from a surface. Here, we investigate bianisotropic metamaterials that can be tailored to have custom angle-dependent emissivity polarization profiles in the near-IR. A genetic algorithm is employed to synthesize an electromagnetic band-gap metamaterial structure that transitions from...
Transformation Optics (TO) has enabled new methodologies for the design and specification of gradient-index (GRIN) lenses for radio-frequency and optical applications by linking refractive index gradients to a mathematically equivalent change in geometry in an alternative (virtual) space. In this work, concepts from classical optical lens design are interpreted through TO. This is demonstrated by...
Infrared (IR) absorbers have been previously studied for use in narrow-band and multi-band applications. Here, we investigate a novel absorber structure based on an electromagnetic band-gap (EBG) metasurface with a curvilinear metallic screen. CMA-ES was employed to determine the coefficients used in the screen generation in order to successfully design an absorber for the near-IR.
The port substitution technique is used to enhance and alter the impedance properties of fixed antenna geometry templates. Generic ports are first introduced into a geometry model, where arbitrary lumped elements can be placed. Next, an impedance matrix is generated through a full-wave simulation technique. The covariance matrix adaptation evolutionary strategy (CMA-ES) is then employed with the port...
Electrostatic properties of two-dimensional nanosystems can be described by their geometry modes. Moreover these modes and their corresponding eigenvalues are invariant under any conformal transformation. This invariance suggests an efficient way for studying transformed structures. Namely, transforming a geometry is equivalent to modifying the strengths of these invariant eigenmodes excited by external...
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