Generation of squeezed light in a nonlinear asymmetric directional   coupler
  We show that a nonlinear asymmetric directional coupler composed of a linear waveguide and a nonlinear waveguide operating by nondegenerate parametric amplification is an effective source of single-mode squeezed light. This is has been demonstrated, under certain conditions and for specific modes, for incident coherent beams in terms of the quasiprobability functions, photon-number distribution and phase distribution. 
Faisal A. A. El-Orany, J. Perina and M. Sebawe Abdalla
quant-ph