Four-wave mixing in a semiconductor laser amplifier

Reports on nearly degenerate four-wave mixing (NDFWM) of two copropagating light waves inside a travelling wave amplifier (1.3 mu m) at input light powers of less than 10 mu W. It describes the first experimental determination of the range of frequency spacing of the two light waves for efficient NDFWM and of the dependence on the state of polarisation.