A vectorlike representation of multilayers
  We resort to the concept of turns to provide a geometrical representation of the action of any lossless multilayer, which can be considered as the analogous in the unit disk to the sliding vectors in Euclidean geometry. This construction clearly shows the peculiar effects arising in the composition of multilayers. A simple optical experiment revealing the appearance of the Wigner angle is analyzed in this framework. 
A. G. Barriuso, J. J. Monzon, L. L. Sanchez-Soto and J. F. Carinena