All-Optical Switch Using Quantum-Dot Saturable Absorbers in a DBR Microcavity

We propose and analyze an all-optical switch based on quantum-dots (QDs) embedded in a distributive Bragg reflector (DBR) cavity. The QDs behave as saturable absorbers that modify the cavity reflectivity. The device exploits the guided in-plane modes of the DBR to fully separate the control pulse from the input signal. We analyze the performance of the switch under realistic experimental conditions. We calculate the signal loss and switching intensity of the device, specializing to the case of InAs QDs embedded in GaAs/AlGaAs DBR structure, and show that the switching power can be as low as 19 μW. Noise injection due to spontaneous emission is also analyzed and shown to be small. We also investigate the possibility of improving the switching speed via nonradiative recombination and show that switching speeds of up to 112 GHz with low energy consumption of 3.91 fJ per bit are possible.