NEARLY DEGENERATE 4-WAVE-MIXING IN DISTRIBUTED-FEEDBACK SEMICONDUCTOR-LASERS OPERATING ABOVE-THRESHOLD

Nearly degenerate four-wave mixing in distributed feedback semiconduct or lasers above threshold is investigated theoretically and experiment ally. The experimental results reveal an almost symmetric amplificatio n of probe and conjugate fields versus frequency with respect to zero pump-probe detuning, in contrast with observations in traveling wave a mplifiers. The result of the theory, based on the coupled mode formali sm, is a set of nonlinear differential equations which are solved in t he mean field approximation. The theory is shown to match well with th e experimental results when the effect of the nonlinear gain compressi on is taken into account.