Multiphoton multimode polarization entanglement in parametric down-conversion

We study the quantum properties of the polarization of the light produced in type-II spontaneous parametric down-conversion in the framework of a multimode model valid in any gain regime. We show that the microscopic polarization entanglement of photon pairs survives in the high gain regime (multiphoton regime), in the form of nonclassical correlation of all the Stokes operators describing polarization degrees of freedom.