111,940 research outputs found
Two-dimensional photonic aperiodic crystals based on Thue-Morse sequence
No full textWe investigate from a theoretical point of view the photonic properties of a two dimensional photonic aperiodic crystal. These structures are obtained by removing the lattice points from a square arrangement, following the inflation rules emerging from the Thue-Morse sequence. The photonic bandgap analysis is performed by means of the density of states calculation. The mechanism of bandgap formation is investigated adopting the single scattering model, and the Mie scattering. The electromagnetic field distribution can be represented as quasi-localized states. Finally, a generalized method to obtain aperiodic photonic structures has been proposed
Electromagnetic waves dynamics in a nonlinear dielectric slab by the method of characteristics
No full textElectromagnetic shock waves are a relatively unexplored field. This paper considers their propagation in the case of a dielectric slab. At first we examine the mathematical problem relating to the physical interpretation of the uniqueness of the solution. A link between uniqueness and irreversibility is pointed out as in the case of shock waves in gasdynamics. Then we illustrate an algorithm, based on the concept of characteristics curves, which gives a very interesting performance
"The non-uniqueness of the surface integral equations for the scattering from perfectly conducting objects"
No full textTunable T-shaped waveguide in two dimensional photonic crystals based on liquid crystals
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A numerical wave-optical approach for the simulation of analyzer-based x-ray imaging
No full textAn advanced wave-optical approach for simulating a monochromator-analyzer set-up in Bragg geometry with high accuracy is presented. The polychromaticity of the incident wave on the monochromator is accounted for by using a distribution of incoherent point sources along the surface of the crystal. The resulting diffracted amplitude is modified by the sample and can be well represented by a scalar representation of the optical field where the limitations of the usual 'weak object' approximation are removed. The subsequent diffraction mechanism on the analyzer is described by the convolution of the incoming wave with the Green-Riemann function of the analyzer. The free space propagation up to the detector position is well reproduced by a classical Fresnel-Kirchhoff integral. The preliminary results of this innovative approach show an excellent agreement with experimental data
The non-uniqueness of the surface integral equations for the scattering from perfectly conducting objects
No full textThe problem of non-uniqueness of the surface integral equations adopted for the determination of the current density over perfectly conducting objects is dealt with. Firstly, the subject is reviewed with reference to a circular cylinder. Then, the case of more scattering objects is investigated and both the strategies for the determination of the non-uniqueness conditions and the countermeasures for facing the problems are given
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