Broadband composite polarization rotator
  We describe a broadband optical device that is capable of rotating the polarization plane of a linearly polarized light at any desired angle over a wide range of wavelengths. The device is composed of a sequence of half-wave plates rotated at specific angles with respect to their fast-polarization axes. This design draws on an analogy with composite pulses, which is a well-known control technique from quantum physics. We derive the solutions for the rotation angles of the single half-wave plates depending on the desired polarization rotation angle. We show that the broadband polarization rotator is robust against variations of the parameters of both the crystal and the light field. 
Andon A. Rangelov and Elica Kyoseva
physics.optics