Four-wave mixing and wavelength conversion in quantum dots

We perform a theoretical analysis based on density-matrix equations to determine the nonlinear susceptibilities and gain coefficients for a quantum-dot semiconductor optical amplifier. Our results show that for a single bound-state quantum-dot, carrier relaxation at large current densities is limited by the carrier capture time from the continuum to the bound state. We then compare our results with experiment and show that there is a significant contribution from carrier heating in the four-wave mixing efficiency. Our results and data fit indicate that efficient four-wave mixing on high-speed signals of greater than 160 Gb/s is possible.