The trilinear Hamiltonian of Tucker and Walls, governing the parametric amplification, leads to three coupled nonlinear Heisenberg equations in terms of creation and annihilation operators. Using the Manley-Rowe relations the equations are reduced to a single nonlinear equation in terms of one of the number operators. Thereafter, it is solved by means of a perturbation method around the diagonal, allowing calculation of the mean number of photons and the variance of the amplified field. The short-time approximation, the parametric approximation, and the classical limit are reobtained by suitable limiting processes.

• Received 8 April 1976

DOI:https://doi.org/10.1103/PhysRevA.15.1157