High saturation behavior of the four-wave mixing signal in semiconductor amplifiers

We show by a simple model that, in semiconductor amplifiers, the functional dependence of the four-wave mixing signal on the output power of pump and probe depends on the underlying optical nonlinearity. The observation, at different pump-probe detunings, of a different dependence of the conjugate power on pump and probe output permits the identification of the dominant optical nonlinearity at a given detuning.