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. 
Julien Laurat (LKB - Jussieu), Thomas Coudreau (LKB - Jussieu, MPQ),   Laurent Longchambon (LKB - Jussieu), Claude Fabre (LK...