With the increasing number and sophistication of quantum well (QW) electroabsorptive devices,1 it has become extremely important to understand the mechanisms responsible for their switching speeds and saturation intensities. We have investigated the dynamics of the photoexcited carriers in a reverse biased GaAs/AIGaAs QW PIN structure. A 6-10-ps laser puise (pump) was used to excite the carriers in a small region of the device, and a time-delayed spatially displaced pulse (probe) was used to monitor the induced changes in the absorption [Fig. 1(c)]. The carriers excited by the pump beam escape from the wells (via tunneling2,3 and/or thermionic emission4,5) and travel to the electrodes, thereby locally reducing the voltage and changing the absorption coefficient. The voltage pulse then decays due to propagation on the surface of the diode, and the initial field in the structure recovers.

© 1989 Optical Society of America

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