OBSERVATION OF CHAOTIC INSTABILITY IN THE ACTIVE-MODE LOCKING OF A SEMICONDUCTOR-LASER

We examine experimentally the consequence of frequency detuning an act ively mode-locked external-cavity semiconductor laser from resonance. We observe a transition of the laser system from a periodic oscillatio n to a nonperiodic state with broadened spectral tones. By estimating the fractal dimension of the corresponding phase-space attractors, we show the presence of low-dimensional chaos. The route to chaos is a we ll-defined regime of three-frequency quasi-periodicity preceded by a t wo-frequency quasi-periodicity.