Long-wave optics

The basis of the near-complete analytical methodology that now exists for the design of long-wave optical systems is set out. The Gaussian beam-mode treatment of free-space propagation is extended to cover the transformations produced by conic-section reflectors or lenses, and both the propagation steps and the lens transformations are incorporated into a matrix formulation readily applicable to networks of such reflectors or lenses. In the process the theorems of Fourier optics are demonstrated and the vectorial properties of the beam-fields are kept explicit. It is shown how recent formulations of partial coherence have made it possible to include partially coherent beams in the same methodology. For the design of high-performance systems, the inclusion of higher-order mode dispersion must be fully understood, the vector properties must be recoverable, and the paraxiality on which the methodology rests must be critically assessed. The authors emphasize these aspects and present a single systematic formulation embracing all the elements