Bistable behaviour in squeezed vacua: I. Stationary analysis

A time-independent theoretical and numerical analysis of an optical bistabl e model of two-level atoms in a ring cavity, driven by a coherent field and in contact with a squeezed vacuum field is presented in the two cases of a bsorptive and dispersive optical bistability (OB). In the former case, a su itable choice of the phase of the squeezed vacuum field reduces the thresho ld for OB to occur compared with the normal vacuum case. In the latter case , regions of OB are identified as one or two disconnected simple closed cur ves depending on the cooperation parameter C-<(>) C-crit(max): C-crit(max) is the maximum possible value of the critical value of C at fixed values of the squeezed vacuum field parameters. Phase switching effects between diff erent (output) states of the system is investigated in detail. In the absor ptive case, one- or two-way optical switching is possible depending on C-<( >) C-crit(max). We also present results which demonstrate more complicated switching behaviour in the dispersive case.