A GEOMETRIC (PANCHARATNAM) PHASE APPROACH TO THE POLARIZATION AND PHASE-CONTROL IN THE COHERENT OPTICS CIRCUITS

The control of the state of polarization and of the phase shift represents an important task in developing coherent optics circuits. The paper introduces a novel control strategy based on the concept of geometric, or Pancharatnam, phase. This phase is topological in nature and it appears when a closed loop is traced on the Poincare sphere. The aspects concerning the polarization control are analyzed for three generic input states: circular, linear and elliptical. For each situation, the evolution of the geometric and dynamic phase is given together with the control circuit design. Similar concepts are applied also to phase control in the coherent detection. The analysis points out that only a design based on the concept of "geometric phase" permits the developing of control systems intrinsically endless.