Effects of spontaneous emission excited state lifetime on the output performance of quantum well lasers

In this paper, we have investigated the effect of spontaneous emission’s excited state lifetime on the output performance of the quantum well laser using quantum well transmission line modelling technique. It has been found that as the spontaneous emission lifetime increases the turn-on transient response of the quantum well laser is delayed, exhibiting the larger peak and steady state arrival times and the laser steady output has larger noise. Meanwhile, the increase in spontaneous emission lifetime leads to the larger peak and steady state arrival times of the carrier density variation during the turn-on process. Also, due to the increase of the spontaneous emission lifetime, the bandwidth and magnitude of the laser steady output spectra increase while the side lobe suppression ratio decreases and there exists a blue shift in the peak wavelength. These studies confirm that the quantum well laser with less spontaneous emission lifetime has more superior output performance (fast transient response, less noise and narrow bandwidth); they also provide an effective method to compare and predict the spontaneous emission lifetimes for different semiconductor optical materials.