Abstract

The use of stationary Bragg-regime reference gratings to enhance the detection of weakly modulated space-time gratings produced by traveling surface acoustic waves (SAW) located at the input plane of the reference grating was analyzed by Magnusson and Black.¹ Their analysis has been extended to include the use of a traveling Bragg-regime reference grating that is spatially separated from a SAW. Furthermore, experimental investigations of this double-grating interaction have been performed. When the m = 0 and either the +1 or –1 fields diffracted by the space-time grating produced by the SAW are symmetrically incident on a traveling Bragg grating of the same spatial period as the SAW, a component of the output intensities oscillates. The frequency of this oscillation is determined by the relative velocity of the two traveling gratings. In the small signal limit, in which the SAW grating is weakly modulated relative to the reference grating, the amplitude of the intensity modulation varies linearly with the modulation amplitude produced by the SAW. Results from experiments using a 100 µm SAW traveling on a LiNbO₃ substrate separated from a 100 µm bulk acoustic wave traveling in a flint-glass acousto-optic modulator are in good agreement with analysis.

© 1990 Optical Society of America