A detailed derivation of the master equation and the corresponding time evolution of the cavity radiation of a coherent beat laser when the atoms are initially prepared in a partial coherent superposition is presented. It turns out that the quantum features and intensity of the cavity radiation are considerably modified by the phase fluctuation arising due to the practical incapability of preparing atoms in the intended perfect coherent superposition. New terms having opposite signs than the contribution of the driving radiation emerged in the master equation. This can be taken as an indication of a competing effect between the two in the manifestation of the nonclassical features. This, on the other hand, means that there is a chance to regain the quantum properties that might have been lost due to faulty preparation in engineering the driving mechanism and vice versa. In light of this, quite remarkably, the cavity radiation is shown to exhibit nonclassical features including two-mode squeezing and entanglement when there is no driving and when the atoms are initially prepared in a partial maximum atomic coherence superposition, contrary to earlier predictions for the case of perfect coherence.

• Received 27 August 2010

DOI:https://doi.org/10.1103/PhysRevA.82.053835