Optical bistability of a composite system induced by a broadband squeezed vacuum

A composite system consisting of a degenerate optical parametric oscillator (DOPO) and N two-level atoms interacting with a broadband squeezed vacuum (SV) centred at frequency \omega_{\rm s} and an input monochromatic pumping field with a frequency \omega_{\rm p} is analysed. The corresponding explicit analytical steady-state solutions in the central mode \omega_{\rm p}=\omega_{\rm s} are derived, and the result displays optical bistability (OB). In addition, the influence of the broadband SV on the bistable behaviour is analysed in detail.