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Femtosecond gain-index coupling in femtosecond nonlinearity measurements of InGaAsP diode laser amplifiers

New theory on measuring gain and index changes in femtosecond pump probe studies suggests a spectral artifact is present which may have obscured the ultrafast response in previous studies of InGaAsP laser diode amplifiers. A femtosecond heterodyne pump-probe technique is implemented using an Erbium-doped stretched-pulse modelocked fiber laser centered at 1.55 gm and used to obtain simultaneous measurements of transmission and phase changes. These results are analyzed considering the spectral artifact and an experimental scheme for eliminating the artifact is discussed. Thesis Supervisor: Erich P. Ippen Title: Elihu Thomson Professor of Electrical Engineering and Physics