Enhanced entanglement in a non-degenerate four-level atom with a parametric oscillator

We discuss the generation and evolution of a macroscopic entanglement light with a subthreshold non-degenerate parametric oscillator, coupled to a vacuum reservoir. The four-level atoms driven by two classical fields interact with the parametric oscillator. The master equation for the cavity modes of the scheme is derived and analyzed, the entanglement properties of the two-mode light generated by this scheme inside and outside the cavity is studied. We show that the light produced by this system is strongly entangled with time evolution inside and outside a cavity.