TRANSIENT GRATING DIFFRACTION FROM AN INTERFACE BETWEEN 2 MATERIALS -THEORY AND EXPERIMENTAL APPLICATION

A general theory for transient grating diffraction from both sides of a single interface is developed. The grating is assumed to have an arb itrary amplitude on both sides of a bound interface with the grating w ave vector parallel to the interface. The specific spatial origin of t he diffracted light is described for both the reflected and the transm itted geometries of diffraction. In the reflected geometry the signal is dominated by diffraction from a region near the interface that is a small fraction of an optical wavelength wide. The transmitted geometr y signal measures primarily the mean bulk properties of the sample. An experimental example of thermal-transient grating diffraction from a YBa2Cu3O7-x/SrTiO3 interface is presented. Model calculations for the experimental data are performed to demonstrate that the approach can b e used to monitor spatially nonuniform transient grating temporal rela xation.