Differential Gain and Damping in High Speed 1.55 Micrometer Quantum Well Lasers,

The use of multiple quantum wells in the active region of semiconductor lasers has been predicted to give rise to large improvements in their intrinsic frequency response. Such improvements arise from the increased differential gain possible in MQW lasers which has been shown theoretically to lead to an increase in the resonant frequency and to a reduction in the damping of the modulation response. A reduction in the damping is important insofar as this determines the maximum intrinsic bandwidth of the device, given no saturation of output power. There have, however been few experimental reports of such improvements in MQW structures. In this paper we present experimental results on a large number of MQW lasers which, firstly, demonstrate the optimisation in the performance of high speed lasers and, secondly, show qualitative agreement with the theoretical predictions.