MUELLER MATRICES AND THE DEGREE OF POLARIZATION

This article shows that only polarizers, retarders, and improper rotat ion Mueller matrices do not decrease the degree of polarization for an y input Stokes vector. On the other hand, a Mueller matrix does not in crease the degree of polarization for any input Stokes vector if and o nly if it has an unpolarized Stokes vector as eigenvector. Furthermore , for any Mueller matrix an unpolarized incident Stokes vector always has the maximum gain in the degree of polarization. It is pointed out that a general Mueller matrix deforms the Poincare sphere (for input S tokes vectors) into an ellipsoid (for output Stokes vectors). Finally, several inequalities involving the input and output degrees of polari zation are derived. (C) 1998 Published by Elsevier Science B.V.