ABSTRACT
A common problem in the propagation of electromagnetic waves is illustrated in figure 3.1. Here we know the field pattern Ψ on a given plane and wish to calculate the field Ψ′ that this produces at some other plane. In conventional ray optics a problem of this type will typically be dealt with using methods such as Fraunhofer or Fresnel diffraction theory, or by applying a technique known as the geometric theory of diffraction. These techniques are valuable, but they do suffer from some practical difficulties.
