  We report the experimental generation of a class of spin-orbit vector modes
of light via an asymmetric Mach-Zehnder interferometer, obtained from an input
beam prepared in a product state of its spin and orbital degrees of freedom.
These modes contain a spatially varying polarization structure which may be
controllably propagated about the beam axis by varying the retardance between
the vertical and horizontal polarization components of the light. Additionally,
their transverse spatial intensity distributions may be continuously
manipulated by tuning the input polarization parameters. In the case of an
analogous biphoton input, we predict that this device will exhibit biphoton
(Hong-Ou-Mandel) interference in conjunction with the aforementioned tunable
mode transformations.
