Resumen: The second-order characterization of a three-dimensional (3D) state of polarization is provided either by the corresponding 3D coherency matrix or (equivalently) by the associated 3D Stokes parameters. The analysis of the polarization properties that are invariant under orthogonal transformations of the laboratory reference frame allows to define a set of six intrinsic Stokes parameters which provides a simplified interpretation of 3D states of polarization in terms of meaningful physical properties. The rotationally invariant properties of 2D states of polarization are straightforwardly retrieved in a consistent way, so that the 2D intrinsic Stokes parameters are constituted by the intensity, the degree of linear polarization and the degree of circular polarization. Idioma: Inglés DOI: 10.2971/jeos.2015.15054 Año: 2015 Publicado en: Journal of the European Optical Society-Rapid Publications 10 (2015), 15054 [5 pp] ISSN: 1990-2573 Factor impacto JCR: 1.199 (2015) Categ. JCR: OPTICS rank: 60 / 91 = 0.659 (2015) - Q3 - T2 Factor impacto SCIMAGO: 0.561 - Atomic and Molecular Physics, and Optics (Q2)