Macroscopic polarization entanglement in type II OPO

The paper reports on the investigation on to which extent the microscopic polarization properties survive at a macroscopic level, in presence of a continuous flux of photons, in a transverse spatially extended system. A prototype device to generate polarization entangled beams is a quadratic crystal in the type II phase matching configuration. The spectral brightness can be increased by means of a resonant cavity (optical parametric oscillator) . Quantum correlations below threshold is calculated analytically taking into account the walk-off effect between the (ordinary polarized) signal and the (extraordinary polarized) idler. In this regime the average of the signal field is zero, but the far-field (FF) intensity distribution is dominated by two undamped rings (quantum images, noisy precursors of the pattern), whose centers are displaced along the walk-off direction. In the first part, the effect of the selection of different polarization components on the Einstein-Podolsky-Rosen correlations is studied; this is a generalization of the first experimental realization of the EPR paradox for continuous variables in an OPO, taking now into account the transverse profile of the filed. In the second part, the correlations in other continuous variables, the Stokes parameters are then analyzed.