Experimental investigation of amplitude and phase quantum correlations in a type II OPO above threshold: from the non-degenerate to the degenerate operation

We describe a very stable type II optical parametric oscillator operated above threshold which provides 9.7 $\pm$ 0.5 dB (89%) of quantum noise reduction on the intensity difference of the signal and idler modes. We also report the first experimental study by homodyne detection of the generated bright two-mode state in the case of frequency degenerate operation obtained by introducing a birefringent plate inside the optical cavity.