title: Separation of coherent and incoherent nonlinearities in a heterodyne pump-probe experiment.
abstract: We demonstrate that the transient coherent nonlinearity (coherent artifact) affecting the pump-probe response of semiconductor optical amplifiers can be experimentally separated from the incoherent transient. The technique is based on measuring the mirror component of the coherent artifact which is a background-free four--wave mixing signal at a different frequency with respect to the transmitted probe in a heterodyne detection scheme. Measurements on amplifiers of different length reveal strong deviations from the commonly expected symmetric shape of the coherent artifact in case of long waveguides.
authors.forename: P
authors.initials: P
authors.lastname: Borri
authors.forename: F
authors.initials: F
authors.lastname: Romstad
authors.forename: W
authors.initials: W
authors.lastname: Langbein
authors.forename: A
authors.initials: A
authors.lastname: Kelly
authors.forename: J
authors.initials: J
authors.lastname: Mork
authors.forename: J
authors.initials: J
authors.lastname: Hvam