Four-wave mixing and rabi oscillations in quantum-dot semiconductor optical amplifiers

Using a self-consistent delay-differential-equation model for the description of the nonlinear light propagation in InAs/InGaAs quantum-dot-in-a-well semiconductor optical amplifiers, we analyze the amplifier in a four-wave-mixing setup in terms of the conversion efficiency. Our model allows us to extract the hierarchy of nonlinear effects that constitute the four-wave-mixing process. We show that spectral hole burning in the quantum-dot medium facilitates wavelength conversion over a spectral detuning of several THz, whereas the effect of carrier heating and global carrier-density pulsations is found to be negligible. Furthermore we show that for high optical field amplitudes the emergence of Rabi oscillations leads to a flattening of the conversion efficiency, potentially allowing for ultra-broadband wavelength conversion and frequency comb generation.