Experimental investigations of two schemes for polarization-direction-insensitive spectral conversion by use of four-wave mixing in a semiconductor optical amplifier (SOA) are reported. One scheme that utilizes an SOA with a linearly polarized signal and a single copropagating circularly polarized pump is, as far as we are aware, the simplest such scheme that has been reported to date. A theoretical analysis of this novel scheme is also presented. Experimental investigations of that scheme are compared with measurements of the performance of a previously proposed scheme, which involves the use of a single SOA and two orthogonal counterpropagating pump beams. We observe that polarization-direction-insensitive conversion is far more efficient in the new scheme described here. Within the observed detuning range, the difference in efficiency between the two schemes is found to increase from 6 to 18 dB as the detuning is increased. The corresponding increase in the difference of the signal-to-background ratio between the two schemes is from approximately 2 to 16 dB.
© 2004 Optical Society of America
Sujit Bandyopadhyay, Yanhua Hong, Paul S. Spencer, and K. Alan Shore, "Simple techniques for highly efficient wavelength conversion with low polarization sensitivity by use of semiconductor optical amplifiers," J. Opt. Soc. Am. B 21, 1023-1031 (2004)