Achromatic change of circular polarization handedness

We present a new kind of achromatic device that can change very effectively the circular polarization handedness. The device is composed of a sequence of traditional half-wave plates rotated at specific angles with respect to their fast-polarization axes. The proposed apparatus is robust to variations in the parameters of both the crystal and the incoming light, these include the crystal temperature, the frequency of the incoming field, the crystal length and the angle of incidence.