Slow light generation through four wave mixing is experimentally investigated in a non-linear semiconductor optical amplifier (SOA). The mechanism of slow-light generation is analyzed through gain saturation behavior of the SOA. The delay of the probe beam is controlled optically by pump-probe detuning. A delay of 260 ps is achieved for sinusoidal modulation at 0.5 GHz corresponding to a RF phase change of 0.26π. © 2011 SPIE.