Abstract
We present simultaneous measurement of femtosecond time-resolved nonlinear phase and amplitude changes aronud the excitonic resonance in a GaAs/AlGaAs quantum well. The nonlinear phase shift is one of the basic mechanisms of ultrafast semiconductor photonic devices. Full information on the time-resolved and frequencyresolved nonlinear phase shift is successfully obtained by means of a novel interferometer, polarization-division Sagnac interferometer (PSI). The PSI has a remarkable advantage of high stability owing to the commonpath configuration. In order to separate the phase and amplitude changes, the optical path difference is scanned between the probe and reference pulses making the best use of polarization. The time dependence of these changes is observed to be determined by the exciton lifetime. The PSI is a powerful method for characterization of ultrafast photonic devices.
