Master-equation theory of multimode semiconductor lasers .2. Injection locking

The master-equation theory for multimode semiconductor lasers [A. Eschmann and C. W. Gardiner, Phys. Rev. A 54, 760 (1996)] is adapted to treat the case of an injection-locked laser. Both the intensity noise and the phase noise of the system are examined. A decrease in the total intensity noise and in the intensity noises of the individual modes is found for increasing injection power, provided the injection signal does not dominate the entire system. A regime is found in which a reduction of the intensity noise below the shot noise level is obtained which is not single-mode squeezing, but which is due to anticorrelations between the individual modes, and a further regime in which true single-mode squeezing exists is also found. The phase noise is found to decrease with increasing injection strength, in other words as phase locking occurs.