Quasi-periodic route to chaos in an actively mode-locked external-cavity semiconductor laser

Laser mode-locking is an effective modulation technique which can be used in fiberoptic link applications. In a semiconductor laser, active mode-locking can be achieved through the direct modulation of the laser at the cavity resonant frequency. If the modulation frequency is detuned from this condition, large optical intensity fluctuations can occur, which can cause a significant degradation in the noise figure of the laser, and consequently in the noise figure of the overall link. In this paper, we investigate the consequence of frequency detuning an actively mode-locked external-cavity semiconductor laser. We experimentally demonstrate the existence of chaos in a mode-locked laser upon frequency detuning. To our knowledge, chaotic instability in an actively mode-locked semiconductor laser has not been reported