Rigorous formula for electromagnetic field power based on Poynting vector.

Abstract: Power of an electromagnetic field in a plane is derived exactly as a function of the angular spectrum of only electric field components at another plane based on Maxwell equations and Poynting vector. Then, this quantity is acquired as a function of the electric field components. In this calculation, a function appears that is general and does not depend on the electromagnetic field function. [Copyright &y& Elsevier]