Theoretical and experimental investigations on the performance of broad-sense quantum-well superluminescent diodes based on the concept of energy level divergence

In this paper, a latest theoretical model for the performance optimization of the broad-sense quantum-well superluminescent diodes (SLDs) based on the concept of energy level divergence (ELD) is presented. The simulation results on the performance of such a kind of devices with GaAs/AlGaAs potential-well structures and ignorable residual facet-reflections show that the ELD concept is truly valid and necessary to be considered in the modelling. It is also found that, for a fixed output power, both the spectral ripple coefficient and the spectral bandwidth decrease monotonically as the well-thickness increases. Moreover, the simulation results are in a pretty good approximation with the experimental ones. Typically, for a 3 mm long and 10 μm wide (referring to the active-region width) device emitting a fixed power of 25 mW and being required to have a ripple-coefficient not larger than 5%, the experimentally determined optimum well-thickness is 90 nm and the simulation one is 87 nm. And, the corresponding spectral bandwidths are 15 nm and 14.8 nm, respectively. It is believed that such a theoretical model could be further improved and eventually worthy for practical use.