Abstract

We report a new type of nonlinear optical effect which results from the transient spatial separation of photoexcited carriers in compositionally graded structures. The lack of inversion symmetry of the structure results in the development of a net voltage. This photoinduced space charge field was measured via the electrooptic effect. We have also observed an enhancement of the effect when the energy of the probe beam approaches an optical transition of the structure. The effect can also be used to examine the transport of free carriers in graded gap structures.

© 1990 Optical Society of America