Approximate yet Confident Solution for a Parametric Oscillator in a Kerr Medium

We study the temporal evolution of a coherent state under the action of a parametric oscillator immersed in a nonlinear Kerr-like medium. Applying a self consistent method we obtain an approximate time evolution operator. This operator behaves like a squeezing operator due to the temporal dependence of the oscillator's frequency. We analyze Mandel's parameter, the presence of squeezing in the field quadratures and the generation of photons from the vacuum state. (paper)