Dark pulse formation in a quantum-dot laser

The laser emission of an InAs/GaAs quantum-dot laser after injection of a n onresonant optical pulse is time resolved using femtosecond upconversion. T he injected pulse burns a hole into the gain spectrum that leads to an ultr afast redistribution of carriers away from the lasing wavelength, thereby g enerating a spatial domain of reduced laser intensity. This domain propagat es through the laser, is reflected at the facets, and thus repeats periodic ally in the output of the quantum-dot laser, forming a train of dark pulses . As a slower response to the optically induced perturbation, gigahertz-fre quency relaxation oscillations are observed. (C) 2001 American Institute of Physics.