NONLINEARITY OF PANCHARATNAMS TOPOLOGICAL PHASE

Since Berry introduced topological phases to describe the adiabatic transport of the spin of particles in parameter space, they have become a practical and descriptive concept for understanding interference phenomena in many quantum mechanical systems. For the photon two different applications of this concept were found in crystal optics: (1) the optical activity of helically wound optical fibers and (2) the development of the state of polarization on the Poincare sphere. We present a remarkable optical ''nonlinearity'' of certain polarizing interferometers, which we discovered by using the concept of the topological phase on the Poincare sphere and we demonstrate it with a simple experiment.