Nonclassical light in complex optical systems

A general method is developed for analysing the evolution of nonclassical light in complex two-mode optical systems where linear and nonlinear processes with quadratic Hamiltonians can take place simultaneously or successively. Analytic expressions are derived for the output Wigner function and the output photon number distribution for a general coherent-state superposition input that can approximate any quantum state of light with a high degree of accuracy. As an example, the evolution of amplitude squeezed light is analysed in a nonlinear coupler with degenerate and nondegenerate parametric amplification. it is shown that all-optical switching can be realized in this system.