Numerical simulation of modal gain in electrically pumped organic semiconductor lasers

摘要

In this article, a model to calculate the modal gain in organic laser diode structures is presented. A single layer design is considered to investigate the dependence of the gain on power density, charge carrier mobility and thickness of the active layer. We show that unequal charge carrier mobilities are detrimental and that there is an optimum active layer thickness of approximately 200 nm, if different devices are compared on the basis of equal power density. Neglecting all losses, the highest calculated gain is 0.7/cm for a power density of P=50 kW/cm2 in our MEH-PPV like model material. Furthermore, the influence of absorption by polarons is quantified. We show that the cross section for this process has to be at least 20 times smaller than the cross section for stimulated emission in order to achieve net gain in the most favourable case that was considered.