EXPERIMENTAL STUDIES ON NONLINEAR DISPERSIVE SURFACE ACOUSTIC-WAVES FOR SOLITONS

Nonlinear dispersive surface acoustic waves propagating: on LiNbO3 sin gle-crystal plates were studied. In order to control the dispersion, a thin SiO2 overlay was applied. Harmonic generation measurements in th e crystals without SiO2 overlay show that the second-harmonic amplitud e exceeds that of the fundamental wave when the initial wave amplitude exceeds 40 Angstrom, and the spatial periodicity length of harmonic g eneration varies depending on power. In the samples with 500-Angstrom- thick SiO2 coatings, no significant change of the periodicity length w ith power has been detected. In both cases we observed an increase of phase velocity with acoustic power. Comparison of the experimental dat a with the spectrum of Korteweg-de Vries solitons suggests the presenc e of surface acoustic wave solitons.