Optical gain in O-band active regions with multiple dot-in-well layers

The optimum number of layers in InAs-based quantum dot-in-well active regions is investigated by means of sophisticated measurements of structures containing 8, 12, and 14 dot-in-well layers. Measurements of optical gain vs a parameter proportional to the carrier density indicate that additional layers do provide a proportional increase in the available gain at a given carrier density. This indicates that unequal optical overlap and unequal electrical pumping of the different layers are not significant effects. It is suggested that performance better than that of the typically used seven or eight layers may occur for samples with a higher layer number with reduced levels of p-modulation doping to minimize internal optical mode loss and non-radiative recombination.