Monitoring of Electromagnetic Energy Flow in a Confined Region of Evanescent Waves by an Alternative Expression for the Poynting Vector

For monitoring of energy flow an alternative expression for the Poynting vector is presented. This expression is an intrinsic integrable function at the boundary problem solution by the method of single expression (MSE). The MSE does not exploit the superposition principle, i.e. does not represent solutions of Helmholtz equation as the sum of counter - propagating waves. This permits to have an alternative expression for the Poynting vector applicable both in media of a positive product of permittivity and permeability and of a negative product that relevant to the region of evanescent waves as well. At the boundary problem solution by the MSE (that is carried out numerically) it is possible to observe spatial distributions in confined media not only for electric and magnetic field amplitudes, but also the Poynting vector. The alternative expression for the Poynting vector in the MSE is in complete agreement with the traditional representation of the Poynting vector.