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Abstract: We investigated optical transparency in ceramics assisted by disordered porous clusters. The structure and statistical properties of three-dimensional (3D) well porous ceramics is studied. Theoretical model based on the percolation theory and numerical simulations are applied to interpret the observed phase transition from an optically opaque state to a transparent state. The porous ceramic samples were fabricated by the technique of slurry casting. The transmission of optical radiation (optical percolation) over the entire porous samples is observed since the critical concentration of porosity was exceeded. We explain this effect by the rising of the spanning cluster inside of the porous structure that produces a network of porous voids. Our experimental results are in good agreement with the numerical simulations. [Copyright &y& Elsevier]

Abstract: We study transmission of the electromagnetic waves of the near infrared spectral range through the metal–semiconductor spherical stack with a radial dependence of the effective dielectric permittivity of semiconductor layers. Such an inhomogeneity is formed by a high concentration of carriers at the interfaces of thin semiconductor–metal structures and its spatial scale can be of order of a width of narrow metallic layers. Because of complexity of analytical solution, we develop numerical approaches, which allow us to study the features of the electromagnetic wave propagation through such a nonuniform structure. The eigenfrequencies and radial distributions of fields are also discussed. [Copyright &y& Elsevier]

We have numerically studied the transmittance of the metallo-dielectric spherical structure deposited on a microsphere in a frequency range where the dielectric permittivity of metal is negative. We have found an equidistant spectrum of the resonant peaks of almost completely transmittency. The position of the peaks is defined by the thickness of the dielectric layer, and the width of peaks sharply decreases with increases thickness of the metallic layer. We have explored the radial distribution of the electromagnetic field in such a stack and the spectrum of the eigenfrequencies. The amplitude of the field in the dielectric layers may exceed on 1 to 2 orders of magnitude the value of a field in the output of the structure. Such an effect opens the opportunity to use the microspheres coating by metallo-dielectric multilayers for an effective surface harmonic generation in the optical range and for a high-resolution frequency conversion in the bands of such resonances. [Copyright &y& Elsevier]

Results of experimental and theoretical investigations of dynamic phenomena, which occur under the three-wave resonant interaction of ultrasonic beams in a crystal TeO2, are presented. The interacting waves are fast longitudinal ultrasonic wave (pump, its frequency is 100–1000 MHz) and two slow co- and counter-propagating transverse ones. When the input intensity of the pump wave exceeds ∼5 times the threshold of parametric generation, a complex spatial-temporal dynamics is observed, both regular and chaotic. The resonant three-wave interaction has been simulated by means of solving coupled equations for slowly varying amplitudes of interacting waves, when a transverse inhomogeneity has been taken into account. The spatial-temporal distributions of wave amplitudes within the crystal are complex in all directions and they qualitatively describe the experimental data. [Copyright &y& Elsevier]