Structure of the set of paraxial optical systems

The set of paraxial optical systems is the manifold of the group of symplectic matrices. The structure of this group is nontrivial: It is not simply connected and is not of an exponential type. Our analysis clarifies the origin of the metaplectic phase and the inherent limitations for optical map fractionalization. We describe, for the first time to our knowledge, an image girator and a cross girator whose geometric and wave implementations are of interest. (C) 2000 Optical Society of America [S0740-3232(00)00102-2] OCIS codes: 080.2730, 000.3870.