Four-wave mixing and asymmetric nonlinear gain in a semiconductor-laser amplifier

Summary form only given. Four-wave mixing (FWM) in semiconductor laser amplifiers (SLA) has been studied extensively in recent years. In the present paper, we report on measurements with beat frequency (Delta f) values up to | Delta f|=600 GHz, which give a much clearer demonstration of the contribution due to intraband dynamics. Moreover, we show, for the first time to our knowledge, that there is an asymmetry in the amplified spontaneous emission (ASE) spectrum, which we attribute to the same nonlinear-gain effect. ASE and the pump wave cause FWM in a similar way as the signal wave and the pump wave cause FWM.