New equivalence theorems for planar sources that generate the same distributions of radiant intensity

It was recently shown that planar sources of entirely different states of coherence may generate fields that have the same intensity distribution throughout the far zone. With the help of a certain new correlation coefficient (which we call the coefficient of directionality), a new formulation of the underlying equivalence theorem is obtained which elucidates, in a very clear manner, the underlying physical principles involved. It is also shown that a quasihomogeneous source may always be specified that will generate the same far-zone intensity distribution as any given finite steady-state planar source. This result is illustrated by several examples. In particular a quasihomogeneous source is described that will generate the well-known Airy pattern intensity distribution.