Influence of co - and counter-propagating light on the phase-mismatch effect in semiconductor optical amplifiers

The phase-mismatch effect, caused by the difference in confinement factor between transverse electric (TE) and transverse magnetic (TM) modes, has not been observed in semiconductor optical amplifiers (SOAs) and is not typically accounted for. In this work, we investigate the characteristics of the phase-mismatch four wave mixing (FWM) effect, which occurs in SOA devices. Our results reveal a sinc-like response in the intensity of co- and counter-FWM conjugates as a function of the detuning shift between interacting beams. It is demonstrated that the coherence lengths between the phase match/mismatch cycles differ between co- and counter-propagating nondegenerate FWM experiments and depend on the amplified TE/TM polarizations of interacting waves aligned with respect to the birefringent axes of SOAs. The coherence lengths between each phase match/mismatch cycle in co-propagation experiments are found to be 1600 and infinite GHz, respectively, compared to 800 and 400 GHz found in counter-propagation experiments

Phase-mismatch dependence of the four-wave mixing effect in semiconductor optical amplifiers

The phase-mismatch effect due to polarization-dependent mode confinement factor has been shown to be not a crucial problem in semiconductor optical amplifiers (SOAs) and is usually not accounted for. The phase-mismatch four-wave mixing (FWM) process in SOA devices is experimentally reported. The results reveal a sinc-like behavior in the intensity of FWM conjugate as a function of wavelength separation between transverse electric (TE)/transverse magnetic (TM) pumps due to induced confinement factors difference. Efficient FWM occurred for a detuning shift of about 500 GHz, limited by phase-mismatch conditions and determined by coherence length required for low and high frequencies to complete a full phase-match cycle. Phase-match FWM with an infinity coherence length can be fulfilled by proper alignments of co-polarized TE/TM modes of input waves with respect to the birefringent axes of the device structure