Chirp in picosecond pulses from diode lasers: Dependence on the modulation conditions and linewidth enhancement factor

This paper reports on the first experimental study in the large-signal domain on the relation between the linewidth enhancement factor α and the frequency chirp of picosecond pulses from diode lasers. The time-bandwidth product is found to be constant over a wide range of operating conditions, in good agreement with theory. Different laser structures in the same material (GaAs) are shown to have significantly different chirp behavior and α parameters, thereby experimentally verifying the structural dependence of the α parameter. Simulations based on the standard rate-equations are also performed, and it is found that considerable chirp can be present even in pulses having time-bandwidth products less than one.