Achromatic polarization-preserving beam displacer.

We present a novel device based on four orthogonal reflections that displaces an optical beam while preserving the state of polarization. The principle of operation is the overall compensation of the phase shifts that s and p polarization components of the light acquire at each reflection. This compensation, which relies on the use of four identical reflectors, is independent of the actual values of the s and p reflection coefficients and thus is independent of the wavelength. Measurements of the polarization-preserving properties with different sets of reflectors and tolerances to misalignments are presented.