Spectral oscillations in a frequency-modulation laser operation - art. no.037201

We show the existence of coherent oscillations in the optical frequency spe ctrum of a laser with internal frequency modulation. Three oscillations ari se in presence of a slight detuning between the modulation frequency and th e cavity axial mode separation and are analogous to collective oscillation modes of a chain of weakly coupled pendula with resonance frequencies sligh tly varying along the chain. Although spectral oscillations are damped due to the finite gain bandwidth of the laser cavity, they can be observed in t he transient dynamics during switch-on of the modulator, or can be resonant ly excited by an external forcing.