A quantitative method of evaluation of phase mismatches and calculation of intensities of diffracted light is described in the paper. The analysis is carried out for the case of the acousto-optic interaction taking place in an acoustically anisotropic medium at Bragg angle of light incidence. An example of the calculation is provided for the particular regime of light diffraction in the single crystal of TeO2 possessing the walkoff angle between directions of acoustic phase and group velocities as large as 74 degrees.
Propagation and reflection of plane acoustic waves in crystals of similar tetragonal symmetry but different grade of elastic anisotropy is examined. The reflection of the waves from a homogeneous and flat boundary separating a crystal and the vacuum in the case of glancing acoustic incidence is investigated. As much as two elastic waves may be reflected from the crystal surface. It is predicted that in the materials with a strong anisotropy of elastic properties, the energy flow of one of the reflected waves propagates in a quasi-back direction with respect to the incident energy flow. It is found that the energy flows of the incident and the back reflected waves are separated in space by the angle as narrow as a few degrees. Analysis proves that the relative intensity of the unusually reflected wave may be close to a unit. A decrease in the grade of the anisotropy in a crystal results in vanishing of the backward reflected wave so that its energy fraction is diminishing down to zero. A regular trend is predicted that the effect of the unusual reflection increases with the growth of the grade of the elastic anisotropy.
ΩPropagation and reflection of plane elastic waves in the acousto-optic crystal tellurium dioxide is examined in the presentation. The reflection of the waves from a free and flat boundary separating the paratellurite crystal and the vacuum is investigated in the (001) and the (110) planes of TeO2 in the case of glancing and inclined acoustic incidence on the boundary. The analysis shows that as much two elastic waves may be reflected from the crystal surface. Energy flow of one of the reflected waves propagates in a quasi-back direction with respect to the incident energy flow unusually reflected wave may be close to a unit in a wide variety of crystal cuts. Possible applications of the examined phenomena in acousto-optic devices are discussed in the presentation.
The paper is devoted to image features based on fractal dimension of a set. The algorithm for calculation of grid empirical fractal dimension (GEFD) of a gray-level image is introduced. The properties of GEFD are investigated using the representation of an original gray-level image by the pyramid of 3-D binary images.
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