Theory of gain, modulation response, and spectral linewidth in AlGaAs quantum well lasers

A number of important issues related to the performance of AlGAs quantum well (QW) semiconductor lasers are theoretically investigated. These include a basic derivation of the laser gain, the linewidth enhancement factor alpha, and the differential gain constant in single and multiple QW structures. The results reveal the existence of gain saturation with current in structures with a small number of wells. They also point to a possible two-fold increase in modulation bandwidth and a ten-fold decrease in the spectral laser linewidth in a thin QW laser compared to a conventional double heterostructure laser.