Achromatic polarization rotator with tunable rotation angle

We theoretically suggest and experimentally demonstrate a broadband composite optical rotator that is capable of rotating the polarization plane of a linearly-polarized light at any chosen angle. The device is composed of an even number of half-wave plates rotated at specific angles with respect to their fast-polarization axes. The frequency bandwidth of the polarization rotator in principal increases with the number of half-wave plates. Here we experimentally examine the performance of rotators composed of two, four, six, eight and ten half-wave plates.