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Herein we present a detailed analysis of the optical response of artificial opal films realized employing a near-field scanning optical microscope in collection and transmission modes. Near-field patterns measured at the rear surface when a plane wave impinges on the front face are presented with the finding that optical intensity maps present a clear correlation with the periodic arrangement of the outer surface. Calculations based on the vector Korringa-Kohn-Rostoker method reproduce the different profiles experimentally observed as well as the response to the polarization of the incident field. These observations constitute the first experimental confirmation of the collective lattice resonances that give rise to the optical response of these three dimensional periodic structures in the high-energy range. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a dispersion equation for 3D photonic crystals made of parallel layers of non-overlapping spheres, valid when both wavelength and separation between layers are much larger than the distance between neighbouring spheres. This equation is based on the Korringa-Kohn-Rostoker (KKR) wave calculation method developed by Stefanou et al. and can be used to predict the spectral positions of bandgaps in structures made of dispersive spheres. Perfect agreement between the spectral positions of bandgaps predicted with our simplified equation and those obtained with the numerical code MULTEM2 was observed. We find that this simplified relation allows us to identify two types of bandgaps: those related to the constitutive parameters of the spheres and those related to the three dimensional periodicity (distance between layers). Bandgaps of the first type are independent of the frequency and the distance between layers, while those of the second type depend only on these two quantities. We then analyze the influence of the constitutive parameters of the spheres on the spectral position of bandgaps for spheres immersed in dielectric or magnetic homogeneous media. The number and positions of the bandgaps are affected by the permitivity (permeability) of the host medium if the spheres have dispersive permitivity (permeability). [ABSTRACT FROM AUTHOR]

We have demonstrated the use of a high-repetition-rate 46.9-nm tabletop laser to characterize diffraction gratings designed for grazing-incidence operation in the soft-x-ray spectral region. The efficiencies for various diffraction orders were measured as a function of angle of incidence and compared with the results of model simulations. This measurement technique provides benchmarks with which to improve electromagnetic codes used in the design of soft-x-ray diffraction gratings. The results illustrate the potential of compact tabletop soft-x-ray lasers for use as a new tool for characterization of short-wavelength optics at the manufacturer's site.

We study surface plasmon polariton excitations and surface shape resonances in a lossy metallic grating with bivalued cavities. The modal formalism is used to solve the diffraction problem for the infinite grating and the homogeneous problem for a single cavity in a plane surface. Both polarization modes are considered. We provide curves of reflected efficiency versus wavelength as well as near-field plots. The resonances are identified as dips in the reflected efficiency, which imply significant power absorptions. Results for various depths of the cavities and for several angles of incidence are shown, where the different types of resonant behavior can be appreciated. Particular attention is paid to the changes introduced by the finite conductivity of the metal in relation to the results obtained for a perfect conductor.

Diffraction of plane waves by a corrugated grating made of a gyroelectromagnetic uniaxial material is set up by using the T-matrix formalism. The fully vectorial treatment presented here is limited in its range of applicability by the use of the Rayleigh hypothesis. The preferred axis of the anisotropic medium is considered parallel to the mean surface of the periodic interface between the medium and the free space. The analysis is exemplified numerically by calculations performed for sinusoidal gratings.

The scattering of electromagnetic plane waves incident upon a random grating whose grooves are not perpendicular to the plane of incidence is studied. The results display a new effect associated with the weak localization of surface electromagnetic waves in random surfaces. This new effect is similar to enhanced backscattering in the sense that a peak in the intensity of the incoherent component of the scattered light is in a direction opposite to the specular direction, but it differs from enhanced backscattering in that this direction does not coincide with the retroreflection direction and in that it is observed in both p and s polarizations.

The surface impedance boundary condition is used to include the effect of high conductivity of meals in the integral theory of perfectly conducting gratings. As an intuitive approach, the diffraction formalism proposed by Petit for the treatment of infinitely conducting gratings in P polarization is extended to highly conducting materials by introducing the concept of equivalent surface current density. Then, integral equations for both polarizations are deduced in a mathematically rigorous way. The new method is used to calculate the efficiencies of sinusoidal gratings at infrared and visible light, and the numerical results are compared with those obtained using Maxwell boundary conditions and also with the perfect conductivity model.

A bare metallic grating illuminated by a plane, S-polarized electromagnetic wave can completely absorb one of the diffracted orders. These strong absorptions have been reported to be accompanied by two different types of behavior. Here we calculate, by means of an exact differential method, the phase versus angle-of-incidence curves for cycloidal metallic gratings with different groove-depth-to-period ratios. We show that an algorithm based on the electromagnetic theory of gratings can account for the experimentally observed behavior in the vicinity of a resonant anomaly. We also show that this type of study provides additional information about the position of the zeros of the scattering matrix in the complex plane.