UNIVERSAL NORMAL-FORM DESCRIPTION OF SQUEEZING AND INSTABILITIES IN 2-PHOTON PROCESSES

We consider a class of optical systems, consisting of an electromagnetic resonator, a two-photon medium and a single-mode cavity field, in the limit when the field decay constant out of the cavity greatly exceeds the remaining relaxation rates. Under rather general conditions, this limit favors the emergence of self-oscillations over a finite domain of parameter space where, for resonant interaction, the instability has a pure phase or amplitude character. The squeezing of the quadrature component of the output field that is orthogonal to the unstable component approaches the ideal limit in the vicinity of the instability threshold and its spectrum can be described by a simple and universal normal-form. We analyze selected configurations of experimental interest and identify a new type of instability that should emerge in four-wave mixing cavities with a concomitant large squeezing effect; we show also that the phase instability and squeezing recently predicted in two-photon optical bistability persist even after inclusion in the model of the effects associated with the intensity-dependent Stark shift. © 1990.