Shadow radiation: Relations between Babinet principle and Physical Optics

For a three-dimensional (3-D) problem, this paper shows that the Babinet Principle (BP) can be seen as a good approximation of Physical Optics (PO) for the shadow radiation. Indeed, an original demonstration of the shadow contour theorem (from Ufimtsev) is given which shows that the shadow component of PO does not depend on the shape of the object, but only on its contour. Moreover, we also show mathematically that the reflected component of PO vanishes in the forward scattering (FS) direction. Simulations are provided to illustrate the link between the BP and the PO.