Место издания:Saint-Petersburg State University of Aerospace Instrumentation (Russia) Saint-Petersburg, Russia
Первая страница:38
Последняя страница:38
Аннотация:Acousto-optic devices are widely used in spectroscopy, signal processing, modulation, etc. [1-2]. Improvement of acousto-optic devices performance is a problem of current importance which requires comprehensive knowledge of acousto-optic device characteristics. For more detailed investigation of acousto-optic cell's characteristics it is useful to know values of acousto-optic figure of merit not only in the basic planes of a crystal but also in any chosen direction. Many other cuts and geometries of acousto-optic interaction should be investigated. Also the investigation of unpolarized beam modulator may be carried out by comparing figure of merit values for ordinary and extraordinary light beams along a given direction.
The acousto-optic figure of merit is a coefficient of proportionality between acoustic power and diffraction efficiency during light and sound interaction. It is necessary to find directions of light and sound propagation in a crystal corresponding to maximal values of the acousto-optic figure of merit. Finding the optimal value by a simultaneous variation of these light and sound directions is a resource-consuming task. Therefore, development of a quick and precise method providing calculation of the figure of merit is a problem of current importance in acousto-optics. The common approach of the acousto-optic figure of merit calculation is based on solution of the Fresnel equation under the assumption that a direction of light propagation is given. This method may be applied only to isotropic media and to uniaxial crystals. Key idea of the proposed method is based on consideration of the Fresnel equation as an equation for the third component of the refraction index vector assuming that two other components of this vector are given. In this case, it is possible to consider not only the uniaxial crystals but also biaxial crystals. The aousto-optic figure of merit is calculated for arbitrary direction of light propagation in a crystal at a given direction of acoustic wave. In this way, a spatial distribution of the acousto-optic figure of merit is obtained. The distribution shows the acousto-optic figure of merit dependence on azimuthal and polar angles of the incident light direction.
Results of the carried out calculations based on the proposed method were compared to literature data for such materials as tellurium, paratellurite and lithium niobate [3-6]. Good agreement between the obtained results of the calculations and the literature data approves applicability of the proposed calculation method.