Displacement of a monochromatic light beam parallel to itself without change of polarization

Abstract

A light beam can be displaced parallel to itself by two reflections from a pair of parallel mirrors. In general, this simple and often-used arrangement introduces a spurious change of polarization that accompanies the displacement. To eliminate this side effect, film coatings can be used. We show that it is possible to make the polarization changes associated with the two individual reflections mutually compensating by a single film coating of appropriate thickness for each mirror. A polarization-preserving pair of beam-displacing parallel mirrors of dielectric-coated metallic substrates is illustrated. This concept also provides a solution to the problem of design of polarization-preserving axicon reflectors.