# Browsing by Author "Landy, N"

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Item Open Access Going beyond Axisymmetry: 2.5D Vector Electromagnetics(2012-10) Urzhumov, YA; Landy, N; Ciraci, C; Smith, DRLinear wave propagation through inhomogeneous structures of size R≫λ (Fig.1) is a computationally challenging problem, in particular when using finite element methods, due to the steep increase of the number of degrees of freedom as a function of R/λ. Fortunately, when the geometry of the problem possesses symmetries, one may choose an appropriate basis in which the stiffness matrix of the discretized problem is block-diagonal. A particular scenario is the case of a cylindrically-symmetric geometry, where an appropriate basis is the set of cylindrical waves with all possible azimuthal numbers (m). Each of the excited cylindrical harmonics propagate through the structure independently of all other harmonics, and therefore the fields associated with that harmonic can be found by solving an essentially two-dimensional PDE problem in the ρ-z (half)-plane. The cylindrical waves have a prescribed dependence on the azimuthal angle variable (φ), hence the name – 2.5D electromagnetics. This novel approach is applied to the problem of cloaking and wave scattering off a spherical nanoparticle on metallic and/or dielectric substrates.Item Open Access Isotropic-medium three-dimensional cloaks for acoustic and electromagnetic waves(Journal of Applied Physics, 2012-03-01) Urzhumov, Y; Landy, N; Smith, DRWe propose a generalization of the two-dimensional eikonal-limit cloak derived from a conformal transformation to three dimensions. The proposed cloak is a spherical shell composed of only isotropic media; it operates in the transmission mode and requires no mirror or ground plane. Unlike the well-known omnidirectional spherical cloaks, it may reduce visibility of an arbitrary object only for a very limited range of observation angles. In the short-wavelength limit, this cloaking structure restores not only the trajectories of incident rays, but also their phase, which is a necessary ingredient to complete invisibility. Both scalar-wave (acoustic) and transverse vector-wave (electromagnetic) versions are presented. © 2012 American Institute of Physics.Item Open Access Relaxation approach for the generation of inhomogeneous distributions of uniformly sized particles(Applied Physics Letters, 2010-07-12) Hunt, J; Kundtz, N; Landy, N; Smith, DRFor many applications in gradient index devices and photonic crystals, it is necessary to be able to design semicrystalline distributions of particles where the lattice constant of the distribution is an arbitrary function of position. We propose a method to generate such distributions which is physically motivated by a system of interacting particles, and apply it to the design and implementation of a microwave gradient index lens. While the demonstration was preformed at microwave wavelengths, this technique would also be particularly useful for designing devices for operation at IR and visible wavelengths where the fabrication of distributions of uniformly sized holes or columns is very easy. © 2010 American Institute of Physics.