All-optical NOR and XNOR logic gates at 2 Tb/s based on two-photon absorption in quantum-dot semiconductor optical amplifiers

Two-photon absorption (TPA) is a nonlinear absorption process in semiconductors, creating a fast phase change in a low-intensity probe beam. Placing quantum-dots (QDs), on the other hand, in the active region of semiconductor optical amplifiers (SOAs) results in SOAs shorter carrier recovery time and lower gain saturation. Thus, in this article, the physical advantages of both TPA and QDs have been combined to numerically investigate the performance of all-optical NOT-OR (NOR) and exclusive-NOR (XNOR) logic gates, incorporating in Mach–Zehnder interferometers at a data rate of 2 Tb/s. The output quality factor (QF) of the considered Boolean functions against the key operational parameters is assessed and examined, including the impact of amplified spontaneous emission in order to obtain more realistic results. The overall QF in the presence of TPA is always higher than that without TPA.