Dynamics of four-wave mixing in flared-waveguide semiconductor optical amplifiers

A detailed investigation of the performance of four-wave mixing (FWM) in non-flared- and flared-waveguide semiconductor optical amplifiers (FW-SOAs) has been reported. A standard rate equation model has been used which considers the effect of the distribution of carrier density of the transverse direction based on numerical calculation along with the nonlinear Schrödinger equation (NSE). The results have been reported in saturated and unsaturated states of the FW-SOAs. Features of the FWM pulse, such as peak pulse deviation, pulse width, and pulse energy along the length of the SOA cavity have been studied and compared in detail for three waveguide geometrics (non-flared, linearly flared, and exponentially flared). Evolution in time and spectral domain of the FWM pulse has been shown for three different structures. It has been found that the FW-SOAs perform better under saturated regime since the FWM pulse has less distortion compared to the non-flared SOA. In an FW-SOA, pulse-width variations of the FWM pulse are almost insignificant whereas in the non-flared SOA, the FWM pulse suffers from broadening.