We investigate the lateral displacement (Goos-Hänchen lateral shift) of a linearly polarized Gaussian beam
reflected from a corrugated surface between a conventional dielectric and a homogeneous isotropic metamaterial
with a negative index of refraction. We pay particular attention to effects associated with the resonant excitation
of surface plasmon polaritons. The dependence of the lateral displacement on the incident beam parameters is
examined in detail and discussed in different situations among which is the total reflection case. We compare these
characteristics with the limiting case of reflection of a beam from a surface with infinitely periodic corrugations.
Recent advances in the comprehension of the growth dynamics of colloidal crystal films opens the door to conscious
design of experiments aiming at fabricating lattices in which the density of intrinsic defects is minimized. Since such
imperfections have a dramatic effect on scattered light of wavelength smaller than the lattice constant, the evaluation of
the experimental optical response at those energy ranges, based on the comparison to rigorous calculations, is identified
as the most sensitive guide to accurately evaluate the progress towards the actual realization of defect free colloidal
crystals. The importance of the existence of a certain distortion becomes particularly relevant at the above mentioned
energy range. We have thoroughly analyzed the effect of fine structural features on the optical response to conclude that,
rather than the generally assumed FCC lattice of spheres, opal films are better approximated by a rhombohedral
assembly of distorted colloids. Interparticle distance of actual colloidal crystals coincides with the expected diameter for
spheres belonging to the same close-packed (111) plane but differs significantly in directions oblique to the [111] one.
We perform a theoretical study on the group velocity for finite thin artificial opal slabs made of a reduced number of
layers in the spectral range where the light wavelength is on the order of the lattice parameter. The vector KKR method
including extinction allows us to evaluate the finite-size effects on light propagation in the ΓL and ΓX directions of fcc
close-packed opal films made of dielectric spheres. The group is index determined from the phase delay introduced by
the structure to the forwardly transmitted electric field. We show that for certain frequencies, light propagation can either
be superluminal -positive or negative- or approach zero depending on the crystal size and absorption. Such
anomalous behavior can be attributed to the finite character of the structure and provides confirmation of recently
emerged experimental results.
The differences between the resonant response of metallic and metamaterial gratings, both supporting surface polaritons,
evidence the different kind of interference processes occurring between the fields radiated by the surface polariton and
the fields reflected by the surface without corrugation. As in any resonance phenomenon, complementary information can
be obtained by studying the associated homogeneous problem, i.e., by finding the characteristics of the electromagnetic
eigenmodes supported by the corrugated interface. In this paper we solve this associated homogeneous problem, showing
how a periodic corrugation affects the characteristics of surface polaritons propagating along the interface between a
conventional dielectric medium and a metamaterial medium with a negative index of refraction.
We examine quasiperiodic multilayers arranged according to m-bonacci sequences that combine ordinary positive index materials and dispersive metamaterials with negative index in certain frequency ranges. When the averaged refractive index, in volume, of the multilayer equals zero, the structure does not propagate light waves and exhibits a forbidden band. In this contribution we recognize some approximated analytical expressions for the determination of the upper and lower limits of the above mentioned zero-average refractive index band gap.
We explore the electromagnetic response of one-dimensional photonic crystals containing slabs of uniaxial
anisotropic indefinite metamaterials (IMMs) with hyperbolic spatial dispersion characteristics. A band structure
classification has been previously made according to the sign of the permittivity and permeability parameters
for the particular case of optical axis perpendicular to the slab interfaces. To extend this study, here we analyze
how the dispersive behavior of each constitutive parameter affects the multilayer band structure. We consider
two orientations of the optical axis, perpendicular and parallel to the slab interfaces, and TE and TM modes.
Particular attention is paid to the effects of material dispersion on the existence of non-Bragg band gaps.
We investigate the appearence of non-Bragg band gaps in 1D fractal photonic structures, specifically the Cantor-like lattices combining ordinary positive index materials and dispersive metamaterials. It is shown that these structures can exibit two new type of photonic band gaps with self-similarity properties around the frequencies where either the magnetic permeability or the electric permittivity of the metamaterial is zero. In constrast with the usual Bragg gaps, these band gaps are not based on any interference mechanisms. Accordingly, they remain invariant to scaling or disorder. Some other particular features of these polarization-selective gaps are outline and the impact on the light spectrum produced by the level of generation of the fractal structure is analyzed.
We study the diffraction of electromagnetic waves at periodically corrugated isotropic-gyroelectromagnetic surfaces, in the index-matching situation, when the plane of incidence forms an aribtrary angle with the main section of the grating ("conical mounting"). It is shown that, under these conditions, eigenmodes can be excited at certain angles of incidence, which can be calculated. We analyze the variation of the position of the anomalies when the orientation of the plane of incidence is varied, for different orientations of the optic axis and different wavelengths.
Due to the excitation of surface plasmons, the diffuse background of a microrough metallic grating can present intensity maxima called diffuse light bands. We reexamine this phenomenon within the framework of recent studies on photonic surfaces and show that it provides an experimental technique for mapping the dispersion relation of surface plasmons, including the gap that, under appropriate circumstances, opens up in the reciprocal grating space.
We study the relation between the excitation of eigenmodes at isotropic-gyroelectromagnetic flat interfaces under index-matching condition and the singular behavior of the reflectivity at grazing incidences. We show that, as in the isotropic case, these eigenmodes can be excited by waves at other angles of incidence by introducing a periodic corrugation to the interface between the two media. The coupling produces strong peaks in the curves of reflectivity versus angle of incidence, whose intensity and shape depend on the height of the corrugation. Numerical examples for a particular orientation of the optic axis are presented.
We analyze the diffraction of a plane wave by a diffraction (surface-relief) grating
made of an isotropic negative phase-velocity material. Three different
approaches are employed, and the results are compared with those
for conventional (i.e., positive phase-velocity) materials. Resonant excitation of
surface waves on the new types of gratings is examined.
The difference in the curves of the zeroth order cross- polarization reflection coefficients vs. angle of incidence have remarkable potential for application in scatterometry since, if larger than the measurement error, could allow for a reliable nondestructive technique to detect asymmetries in grating profiles. In this paper the cross-polarization efficiencies of metallic gratings with asymmetric grooves are investigated theoretically by means of a rigorous electromagnetic code. The result show that the differences between p yields s and s yields p conversion efficiencies tend to be undetectable for highly conducting materials, limiting, in principle, the application of this potential detection technique.
We study the scattering of electromagnetic waves at lossy metallic rough surfaces with bivalued cavities. In this particular kind of scatterer two resonant mechanism of very different nature can manifest themselves to produce highly selective reflectivity responses: i) surface plasmons and ii) resonant microcavities. To separate the contributions from each resonant mechanism, we compare the results obtained for two different problems: the diffraction problem for infinitely periodic grating with cavity like grooves and the homogeneous problem for a plane surface with a single cavity.
We presents a new coordinate transformation that extends the applicability of the differential method for grating analysis proposed by Chandezon et al. The new transformation is particularly well suited for dealing with grating profiles given by parametric equations. It allows us to treat rather arbitrary profiles, which cannot be straightforwardly modeled with the conventional differential method.
We demonstrate the use of a 46.9 nm tabletop laser in characterizing diffraction gratings designed for grazing incidence operation in the soft x-ray spectral region. The efficiencies for different diffraction orders were measured as a function of angle of incidence and compared with the results obtained using rigorous electromagnetic model simulations.
In this work, we study the homogeneous problem, corresponding to a periodically corrugated surface which separates a uniaxial crystal from a metal. In order to analyze, in a second stage, the excitation of plasmons in conical mounting, we consider that the propagation direction of the plasmons is arbitrarily oriented.
In this paper we solve the homogeneous problem of an almost closed cavity in a ground plane, where the shape of the cavity is described by a multivalued function. To solve this proem we find numerically the complex depths of the cavity for which the determinant of the scattering matrix vanish. These zeros correspond to the resonant frequencies of the cavity; the real part represents the depth at which the resonance takes place, and the imagery part acknowledges for the quality of the resonances. We consider the excitation of the two lowest eigenmodes of each cavity and show that the complex resonant depths coincide with the anomalies present in the diffraction reasons of an infinite gratin formed by this kind of cavities.
KEYWORDS: Light scattering, Scattering, Near field, Light wave propagation, Radio propagation, Electromagnetism, Polarization, Target recognition, Near field optics, Metals
We study the scattering of light from almost closed cylindrical cavities ruled on a highly conducting flat surface. We consider the case where the shape of each cavity can be described by an arbitrary multivalued function of the coordinates. By using the multilayer modal method, which combines the multilayer approximation with the R-matrix propagation algorithm, we investigate the electromagnetic response of this kind of scatterer when it is illuminated by s or p polarized plane waves. Our results show that for both polarizations this system exhibits a resonant behavior manifested by sharp variations in the curves of scattered intensity versus wavelength which are associated with strong intensifications of the near field. The wavelengths at which the resonance occur are intimately connected with the eigenmodes of a single cavity.
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