In this paper it is shown that there is an optical phase transition in the systems of two level atoms and photons, with large detuning and under counter-rotating wave approximation. Our calculations show that such system, even under this approximation have two independent optical phases, the well known  normal and super-radiant ones. In the normal phase, the ground state of the total Hamiltonian, with a large detuning, is a state for which the mean photon number is zero. On the other hand, when   the atom-photon coupling constant exceeds a critical value, the photon mean number is nonzero when the system is in the ground state, and the system makes a transition to the super-radiant phase. We also show this is a second order phase transition.

Keywords: Counter Rotating Wave, Quantum Optics, Phase transition, Super Radiant

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