Point sources of polarized light generate inhomogeneous fields at the surface of a metallic slab
localized at its vicinity. It is found that the associated k-spectrum contains wave vectors larger than
those corresponding to free oscillations. Consequently evanescent fields are available and surface
plasmons can be excited. With FDTD calculations we prove in detail this effect using a point source
of cylindrical symmetry placed near a silver film. In addition, the interaction of the cylindrical wave
and the metallic surface is analytically described by writing the incident wave in terms of a plane
wave basis. Images of the surface plasmon excited by this source and the field distribution in the
vicinity of the surface are shown.
We present numerical results for the optical response of tunable one-dimensional photonic crystals. Two different (monolithic) superlattices (SL) where studied: InSb/air and Si/air. We explore the tuning of a defect state as a function of the temperature and of the donor concentration. The numerical calculations were performed using a realistic model for the dielectric constant that takes into account the dispersion and absorption due to electrons, holes and phonons. In order to lessen absorptive effects, we have optimized the structure so as to achieve strong sensitivity of the defect state tuning.
When rows of cylinders are periodically removed from a hexagonal array of dielectric cylinders, a new two-dimensional (2D) photonic crystal (PC) arises. The new structure consists of a lattice of vacancies embedded in the initial hexagonal lattice. We called it Suzuki Phase because it remains similar structures discovered in the 60's by K. Suzuki studying alkali halides. A plane-wave algorithm as well as a 2D finite difference-time-domain method has been employed to study the photonic properties of this PC as a function of the filling fraction (f) in the case of high dielectric cylinders ((epsilon) equals 13.6) in air. For TM- modes, it is shown that in a certain range of f an isolated miniband appears in the gap of the initial hexagonal lattice. The miniband, which is created by the coupling of defect states, is described by a tight-binding formalism with two parameters. Also, the frequencies of the two possible vacancy defects in the SP have been obtained and their symmetry analyzed.
We study the resonant excitation of the electromagnetic modes in a planar waveguide of metallic walls - light incident on the guide from the air can transfer energy through the walls exciting normal modes of propagation. It is found theoretically that radiation propagates along the guide while the reflectivity presents a minimum. The energy of the incident radiation can be transferred to the guide almost completely when the thickness dm of the metallic wall is around two times the skin depth. Experimental evidence of the injection of light is presented for the system Ag/Al2O3/Ag that was grown by pulsed laser deposition.
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