Alternative depolarization criteria for Mueller matrices.

It is shown that the currently used depolarization criteria of Gil and Bernabeu [Opt. Acta 33, 185 (1986)] and Cloude [Optik (Stuttgart) 75, 26 (1986)] may produce erroneous results when applied to a special class of Mueller matrices. Alternative criteria, based on the Lorentz singular values of the Mueller matrix, are proposed. The theory underlying the two sets of depolarization criteria is discussed and their performances on experimentally determined Mueller matrices are illustrated.