Achromatic polarization rotator.

What we believe to be a new optical element consisting of a single piece isotropic material with three internally reflecting faces for polarization plane rotation by the angle phi=pi/2 is proposed. The principle of operation is based on the geometrical phase effect, which is different in its origin but produces a similar effect to the circular birefringence. It is shown that the rotator made of polymer as well as silica glasses is not affected by the chromatic dispersion in a visible range.