Shadow radiation for scalar problems: Relations between Babinet principle and Physical Optics

For a two-dimensional (2-D) problem, this paper shows that the Babinet Principle (BP) can be derived from the Physical Optics (PO) approximation. Indeed, following the same idea as Ufimtsev, from the PO approximation and in far-field zone, the field scattered by an object can be split up into a field which mainly contributes in the illuminated zone, and a field which mainly contributes in shadowed zone, which is strongly related to the scattered field obtained from the BP. The only difference relies on the integration surface. We also show mathematically that the involved integral does not depend on the shape of the object. Simulations are provided to illustrate the link between the BP and the PO.