Despite the direct observations of the acoustic waves focusing in different solids [J. P. Wolfe, Phys. Today 48, 34–40 (1995)], the properties of the phonons’ propagation and possibility of these control have not been studied in hexagonal media. To check this statement [U. V. Zubrytski, Z. Tekhn. Fiz. 67, 59–64 (1997)] and obtain striking demonstrations of drastic changes in the phonon focusing patterns at elastic properties, modification of such solids’ phonon focusing is simulated in zinc oxide grown by the hydrothermal method, in the vapor state at and without doping with lithium, and magnetron sputtering, in this paper. Simulation shows that elastic modules modification within the accuracy of available experimental data causes both sharp increasing of the intensities and defocusing of the individual phonon modes. Quantitative dependences of the effect have been established for bulk acoustic waves in the samples investigated. The findings allow one to elaborate not only the equilibrium but the dynamic method to control selectively both intensities and angular distributions of the acoustic energy fluxes in the crystals and thin layers as well. Besides, the elastic constants recovering from the measuring of the focusing factor can be realized. [Work partially supported by the Belarusian Republican Foundation for Fundamental Research.]
The self-channelling of cylindrical light beams versus the excitation density, light frequency, and crystallographic orientation is numerically analysed in GaAs, ZnSe, CdS semiconductors. A comparison ofthe data obtained and reported for diode and streamer semiconductor lasers is made. Made out reversing of the angular anisotropy of the real third order nonlinear optical susceptibility is worthy to be studied for a practical implementation.
Abstract. The simplest derivation of Khatkevich's equation based on Fedorov's mathematics is presented here in view of recent confusions on the subject discussed in the literature. In the development of Khatkevich's theory of acoustic axes the general equation is extended by introducing into consideration piezoelectric interaction. It is shown that the linear piezoelectric effect doubles the order of equation for the degenerated roots in hexagonal media in comparison with that obtained at taking into account pure elasticity only. Method is provided for control of phonon focusing anisotropy by investigation of acoustic axes in the piezoelectric medium. Examples of equilibrium dynamics of the acoustic axes for phonon modes in the temperature range from 4.2 to 500 K in CdS and of the phonon focusing factor in ZnO are supplied.
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