Widely tunable four-wave mixing in semiconductor optical amplifiers with constant conversion efficiency

The conversion efficiency and output signal-to-noise ratio (SNR) of single-pump four-wave mixing (FWM) in semiconductor optical amplifiers (SOAs) is strongly dependent on frequency shift. We examine a scheme for FWM in SOAs that uses two orthogonally polarized pumps. We compare experimentally and theoretically the conversion efficiency and SNR of the orthogonal-pump scheme with single-pump FWM. The orthogonal-pump scheme has nearly constant conversion efficiency and SNR over the 4.5-THz range of frequency shifts measured. Experimental and theoretical results for the conversion efficiency and SNR of the orthogonal-pump scheme agree to within 3.5 dB.