Propagation of Electromagnetic Waves in Parametric Media in the Approximation of Geometric Optics.

摘要

During the passage of waves through media whose parameters are changed in time (subsequently let us call them simply parametric), occur special effects, for example a change in the spectral composition of signal. Therefore to their study traditional approach proves to be inapplicable, and is required special examination, in order to explain the possibility of using the laws of geometric optics. In this case, systematically it is more justified to analyze directly the equations of Maxwell, but not to reduce them for different special cases to one differential equation for certain scalar function, as this frequently is done. Since the approximation of geometric optics does not fit the description of fields in the vicinity of their sources, the usual formulation of the problem of geometric approximation consists of finding the wave process of space, if the value of field on certain initial surface S(o) is known. The latter can be selected in the wave zone of an emitter. It can pass in those regions of space where there is still no perturbation action of heterogeneous and parametric properties of the medium. Surface S(o) is convenient to combine with the position of the wave front (in monochromatic field this is the constant-phase surface).