Mathematical modelling and analysis for the optimization of terahertz optical asymmetric demultiplexers using quantum dot semiconductor optical amplifiers

The carrier dynamics of quantum well and quantum dot Semiconductor Optical Amplifiers (SOAs) were mathematically modelled to compare their use in a Terahertz Optical Asymmetric Demultiplexer (TOAD). It was found that the effective recombination rate in the quantum dot devices was 440 fs which is approximately 1000 times faster than for the quantum well devices. This led to the proposal of a simpler configuration of a TOAD with quantum dot amplifiers. A scheme of using different wavelengths for the control and signal pulses which led to greatly improved contrast ratios was also proposed. The physical design and operational parameters for the quantum dot TOAD were optimized and it was shown to be crosstalk free and not susceptible to patterning effects. Switching using the novel one control pulse configuration was realized up to 250 Gb/s. By reverting to the classical configuration a 4 x 250 Gb/s stream was demultiplexed.