Modulator frequency detuning effects in the FM mode-locked laser

The mode-locking behavior of a homogeneous laser with an intracavity FM modulator changes rapidly and asymmetrically when the modulation frequency is detuned by small amounts from its optimum value. We develop here a simple analysis of these detuning effects. The analysis gives explicit expressions for all aspects of the mode-locking behavior as functions of detuning. A physical interpretation of the analysis also makes clear which physical mechanisms are responsible for the detuning behavior.