Quantum images in optical parametric oscillators with spherical mirrors and Gaussian pump

We perform a study of the quantum image phenomenon appearing below threshol d in the optical parametric oscillator for the near and far field, for the case of a cavity with spherical mirrors and Gaussian pump profile. Because of the finite size of the pump, the whole set of Gauss-Laguerre cavity mode s are coupled and therefore an analytical solution cannot he found. We prop ose a numerical treatment taking into account the mode couplings up to a fi nite order, and using an input-output formalism we evaluate the correlation functions for an arbitrary quadrature component of the signal field in the frequency domain. Major quantum spatial features of the plane-wave pump ca se are shown to persist when the pump waist is progressively decreased to r ealistic experimental values.