Effective bandwidth for FM noise suppression in an injection-locked semiconductor laser

We present an analytical expression for the FM noise spectrum of an injection-locked semiconductor laser, taking the ¿-parameter into account. Under the phase-matched condition the FM noise is shown to be suppressed in an effective bandwidth equal to the locking half-width ¿¿L0 for ¿=0. The effective bandwidth can be made larger by increasing the phase delay of the slave laser, but at the expense of a higher resonance peak.