HIGH-SPEED QUANTUM-WELL LASERS AND CARRIER TRANSPORT EFFECTS

Carrier transport can significantly affect the high speed properties of quantum-well lasers. We have developed a model and derived analytical expressions for the modulation response, resonance frequency, damping rate, and K factor to include these effects. We show theoretically and experimentally that carrier transport can lead to significant low frequency parasitic-like rolloff that reduces the modulation response by as much as a factor of six in quantum-well lasers. We also show that, in addition, it leads to a reduction in the effective differential gain and thus the resonance frequency, while the nonlinear gain compression factor remains largely unaffected by it. We present the temperature dependence data for the K factor as further evidence for the effects of carrier transport. In the presence of significant transport effects, we show that the real limit to the maximum possible modulation bandwidth is much lower than the one predicted by the K factor alone. The differences between the modulation response and relative intensity noise measurements are discussed.