  In this paper we will analyze the propagation of the angular spectrum of the
electromagnetic field through a finite length uniaxial crystal. We solve the
boundary conditions of the fields at an interface of an isotropic medium and an
uniaxial anisotropic medium with the optical axis in an arbitrary direction and
soon after we choose the optical axis in a plane formed by the direction of
propagation (z-axis) and the x-axis . We show how the couplings occur between
the components of the field and in what situations we can give a vector or
scalar treatment for the propagation
